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                          THE BOOK OF THE FLY

------------------------------------------------------------------------




                    MICROBES AND TOXINS
                    by DR. ETIENNE BURNET.
                    PREFACE by PROFESSOR E.
                    METCHNIKOFF

                    _Illustrated, Cr. 8vo, 5/- net._

                              "It is one of those works which French
                              authors seem to be especially skilful in
                              producing—works which, while they treat
                              their subject in the broadest possible
                              way, and in a manner to interest the
                              educated general reader as well as the
                              specialist, and yet at the same time
                              accurate and precise in detail."—_Lancet._

                                               LONDON: WILLIAM HEINEMANN

------------------------------------------------------------------------




                              THE BOOK OF

                                THE FLY


                         A NATURE STUDY OF THE
                         HOUSE-FLY AND ITS KIN,
                       THE FLY PLAGUE AND A CURE

                                   BY

                           G. HURLSTONE HARDY

                        With an Introduction by
                             HALFORD ROSS.

[Illustration: logo]

                                 LONDON
                           WILLIAM HEINEMANN

------------------------------------------------------------------------




                   _London: William Heinemann, 1915_




                                CONTENTS


     CHAPTER                                                   PAGE

             PREFACE BY E. HALFORD ROSS, ESQ., M.R.C.S.,
             L.R.C.P., &C.

          I. A PRODUCT OF HUMAN INSANITATION                      1

         II. IDENTIFICATION OF THE COMMON HOUSE-FLY               7

        III. SOME OTHER FLIES AND THEIR DIVERSE HABITS           16

         IV. MYIASIS AND THE ŒSTRIDÆ                             26

          V. GENERAL LIFE HISTORY                                33

         VI. STRUCTURE OF THE HOUSE-FLY                          43

        VII. DISTRIBUTION AND CONCENTRATION OF FLIES             49

       VIII. NATURAL ENEMIES OF FLIES                            53

         IX. DISSEMINATORS OF DISEASE                            58

          X. REMEDIAL MEASURES; CREMATION OF REFUSE              64

         XI. CONTROL WITHIN THE HOUSE                            71

        XII. SERVICE AND UTILITY OF FLIES                        78

       XIII. A CAMPAIGN OF EFFECTIVE WARFARE, CONCLUSION         84

                  *       *       *       *       *

                                APPENDIX

             DESCRIPTION OF THE WINGATE FLY CHART                89

             TABLE OF WING CELLS AND VEINS                       93

             GLOSSARY INDEX OF TERMS USED                        94

             ALPHABETICAL LIST OF SIXTY FAMILIES                 95

             NUMBERED LIST OF FAMILIES WITH DESCRIPTIVE
             NOTES AND REFERENCES                               108

             ANALYTICAL TABLE OF FAMILIES                       113




                             ILLUSTRATIONS


                                                                 PAGE

       Fig. 1. THE HOUSE-FLY, FEMALE, _Enlarged_                    6

       Fig. 2. THE LESSER HOUSE-FLY, MALE, _Enlarged_               6

      Fig. 2a. THE STABLE-FLY, FEMALE, _Enlarged_                   6

       Fig. 3. WING PATTERNS CONTRASTED                            12

       Fig. 5. METAMORPHOSIS; LARVA, INSTAR, IMAGO                 39

       Fig. 6. APPARATUS FOR THE BREEDING OF GENTLES               81


                   THE WINGATE FLY CHART (APPENDIX)

      Plate I. EXTERNAL PARTS AND CHARACTERS, NAMED                88

     Plate II. ANTENNÆ, MANY-JOINTED TYPES                         97

    Plate III. ANTENNÆ, THREE OR FEW-JOINTED TYPES                 99

     Plate IV. WINGS, TYPE-FORMS OF NEMOCERA                      101

      Plate V. WINGS, OTHER TYPE-FORMS                            103

     Plate VI. DETAILS OF SPECIAL CHARACTERISTICS, ETC.           105

    Plate VII. DITTO                                              107

   NOTE. Fig. 4 has been found to be not available for this edition.

------------------------------------------------------------------------




                                PREFACE


The dangers of house-flies to the health of the community have come into
such recent prominence that the appearance of Major Hurlstone Hardy's
book should fill a want. It is written lucidly and clearly, yet in that
popular style which is so frequently lacking in scientific works. This
is a great advantage. Too often scientists are prone to bring out works
couched in terms which cannot be understood by an interested public that
is not versed in technical terms. Thus matter which is of the greatest
general importance is passed unread by many, and is, in consequence, not
acted upon.

Major Hardy has a knowledge of these deadly insects which, in my
opinion, is unsurpassed, because he has the personal experience of
practical experiment combined with the instincts of the naturalist. The
result is an account both accurate and interesting which should prove of
the greatest value.

The discovery of the transmission of disease by mosquitoes required the
passage of a decade before its essentials were grasped by the public
mind; that of the prevention of small-pox required a century. But the
dangers of house-flies is rapidly becoming known in consequence of the
popular literature, which is growing, describing the details of the
lives of these loathly creatures. In this way only can such knowledge be
spread—a knowledge which must become general before flies and the
maladies they convey can be generally and satisfactorily dealt with. It
is of little use to make great discoveries and then to hide them on the
musty bookshelves of learned societies. Instead, they should be adapted
to practical purposes applied for the good of suffering humanity; and
the best way to do this is to bring out well-written, interesting, and
easily read books of this kind, so that all who run may read and their
readings endure. This book should assist much to accomplish this end.
Thus we may look forward confidently to the day when house-flies, and
the diseases they carry, are things of the past. The "Book of the Fly"
must take its place in the history of the events which are to lead up to
the winning of that goal.

                                                            HALFORD ROSS

                        (_of the John Howard McFadden Researches at the_
                             _Lister Institute of Preventive Medicine_).

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                          THE BOOK OF THE FLY




                               CHAPTER I

                   THE HOUSE-FLY, A PRODUCT OF HUMAN
                              INSANITATION


With the present day zeal for popularising interest in common things
(called nature study) there has arisen the demand for knowledge
practically useful and thoroughly up-to-date, yet in a form free from
much of the technical terminology and treatment which are essential in
the student's more fully developed scientific handbook.

The "House-fly" is a fit subject for a simplified study of this kind,
and the present booklet is an attempt to afford information very
different to that of the "popular" works, which only were accessible to
the writer's hands between fifty and sixty years ago; the writers of
those old books all followed the lead of the reverend and learned
contributors to the famous and monumental "Bridgwater Treatises." "The
Wonders of Nature explained," "Humble Creatures" (a study of the
earth-worm and the house-fly, in popularised language), "The Treasury of
Knowledge," "Simple Lessons for Home Use," were the kind of cheaper
works in touch with a past generation; these latter and other later
well-intended publications will now be found to be somewhat deficient or
even a little misleading entomologically; they abounded in pious
sentimentality and mostly attempted an aggravatingly grandiose literary
style, but all have rather failed in teaching practical economic
utility, in connection with which nature-knowledge can be rendered as
interesting as any other kind of instructive literature. The tribe of
two-winged flies, in particular, has not even yet received a full and
adequate study by scientists. A preference has ever been shown towards
those other branches of entomology, which may be more interesting to the
cabinet-specimen collector, but which cannot pretend to have an equal
hygienic and economic importance to humanity.

The presence of the house-fly in our dwellings is often submitted to as
an irritating but an inevitable nuisance; yet very certain remedial
measures would almost exterminate the creature, which is a dangerous and
filthy peril. To many people it will seem a most incredible exaggeration
when told that it is really worse than any one of the less common
creatures universally regarded with horror and disgust as pestiferous
vermin. The surmise may be true that the disgusting body louse carried
bacteria, which spread the "black death"; and, even though the rat's
flea has been found to be the carrier transmitting bubonic plague, yet
amongst people living now in civilised communities within the temperate
zones these parasites cannot be ranked as dangerous equally with the
house-fly. The modern crusade against the house-fly is not based on any
such new discovery, as is that against the mosquito gnats, which are the
means of spreading zymotic diseases mainly in the tropics. The malignity
of the fly is recorded in most ancient history and folk-lore, yet not
very long ago there prevailed amongst certain classes opinions very
different to those of old as well as to those of the present day. A
short anecdote will perhaps amuse as well as explain those misplaced
sentiments, which have not quite died out.

In the middle of the last century there was a boy, thought to be too
delicate to be sent to school, who early earned for himself the
character of being a strange child. When barely more than nine years old
he visited an Aunt who was a veritable exemplar of genteel breeding and
propriety after the early Victorian pattern. There he was seriously
reprimanded for the "cruelty" of feeding his secret pets, which were
garden spiders, with flies which were, so the Aunt said, "poor innocent
creatures made by God for a useful purpose," but, she inconsequentially
added,—"Spiders were horrid." The strange child replied that the Devil
made the flies, and that God made the spiders to eat them. The
astonished Aunt then elicited the fact that the strange child's father
had explained, during a Sunday Bible lesson, that Beelzebub (the Devil)
meant Lord-of-flies.

This strange child was taken a walk over Doncaster Heath by the Aunt's
maid. There a dead rabbit was seen from which maggots were crawling, and
the maid explained that it was fly-blown. Next they both stroked and
patted a patient donkey, and the strange child observed maggots rolling
out of the donkey's nostril[1] on to the ground; he wondered much that
live animals should be fly-blown. He also saw with pity some cows,
around whose eyes flies clustered.

Pondering on these matters, one day he confided to the Aunt his
confirmed opinion in these words—"It seems, Aunt, to me that people who
won't kill flies deserve to be fly-blown." Doubtless, it would have been
better if he had expressed himself thus—People who will not kill fleas
deserve to be flea-bitten; and people who will not wage war against
flies deserve to be fly-tormented. However, the horrified Aunt mistook
the observation for insult and impudent rebellion, and what ensued need
not be related as pointing no useful moral. The strange child was merely
a genuine early nature student ahead of the times by some fifty or sixty
years. In due course he learnt a more orthodox account of "Creation,"
and the existence of mysteries in facts physiological and spiritual,
which can only be imperfectly comprehended in this world.

His craving for nature study was not satisfied with the reading of most
of the cheap books then published for the diffusion of knowledge.
Collecting butterflies and moths sufficed for some of his schoolfellows
in later years, but, not then having access to really good handbooks, he
became an original investigator in wide fields of nature study, and thus
learnt that many statements and opinions, which ordinarily even at the
present day pass current as facts, are erroneous and misleading.
Accordingly, the reader need not be surprised at some statements in the
following pages at variance with what may be met with elsewhere.

Footnote 1:

   Stevens' Book of the Farm and many other publications describe the
  similar affliction of sheep by _Œstrus ovis_ but omit to notice the
  case of the donkey, which I have witnessed several times, but have
  never seen a horse or pony thus afflicted. There is a fly termed
  _Œstrus nasalis_, of which the victimised host is uncertain, for
  Linnæus was mistaken in stating that the larvæ are found in the
  _fauces_ of "horses, asses, mules, stags, and goats," _entering by the
  nostril_.

The old fanciful dogma that everything existing was actually created "in
the beginning," and "for a purpose," was once ardently championed as
controverting aggressive Voltairean atheism, but it must be now
recognised as an unwarranted assumption, deduced from an orthodox
doctrine of "design," which in itself seems acceptably agreeable with
the idea of unity, consistency, and perfection in Creation and The
Creator. In fact the said "fanciful" dogma never really was an integral
part of Christian Catholic doctrine. The house-fly, as we know it, is
absolutely the developed product of human insanitation; scientifically
and practically it is a new "species" of an old "genus" established by a
long course of breeding in man-made environments.

[Illustration: Fig. 1. The House-Fly, Female, _Enlarged_.]

[Illustration: Fig. 2. The Lesser House-Fly, Male, _Enlarged_.]

[Illustration: Fig. 2a. The Stable-Fly, Female, _Enlarged_.]




                               CHAPTER II

               THE IDENTIFICATION OF THE COMMON HOUSE-FLY


Although there are several other kinds of flies which occasionally visit
the dwellings of mankind, there is one super-abundant species, _Musca
domestica_, to which the name of "house-fly" pre-eminently belongs. In
the scientist's discriminating judgment, when viewed microscopically, it
differs substantially from others; but it differs very little in general
appearance from certain outdoor flies and from one not uncommon indoor
smaller companion, _Fannia canicularis_, which is not classified amongst
the _Muscidæ_ but amongst the _Anthomyidæ_. This latter has been fitly
termed the "lesser House-fly;" it has the same habit of delighting to
pester man as much as or more than cattle outdoors. Both these flies
join with several others in frequenting stables and cow-sheds.

These two flies and the familiar "blue-bottle" (again it seems that we
are liable to confuse two species) are the special subject of our
present study; but it will be as well to take passing notice of some few
other members of the tribe classified by scientists as belonging to the
order _Diptera_. The species of this order native to Great Britain are
said to number nearly three thousand, of which quite two hundred of
largish sizes are exceedingly common and widely distributed. This order
is characterised by the fact that all the species are furnished with one
pair of wings only:— dis = double, pteron = wing; they all undergo a
metamorphosis analogous to that of four-winged insects.

The dipterid flies are apt to be popularly recognised as flies (with fat
bodies) and gnats (with slim bodies); but they may be more intelligently
classified (with a few anomalous exceptions) as flies (_a_) having a
trunk-like mouth or proboscis (miscalled a tongue), terminating with
bilobed suctorial lips, and as flies (_b_) having a bayonet-like trunk,
or a sheaf-like tubular spike with skin-piercing lancets. No two-winged
flies have stings; the tail of the female, which terminates with the
ovipositor and is retractile in a telescopic manner, is very soft and
quite unlike the sting of the ichneumon or the ovipositor of the
"saw-fly," both of which possess two pairs of wings like bees and wasps,
and therefore are classified with the insect race called _Hymenopteræ_.

Omitting _Aphides_ (green-flies, plant-lice, and the like) which are an
"order" by themselves, and excluding gnats of slim form, mosquitoes, and
midges, which are mainly crepuscular, nocturnal, or shade frequenting,
we might try unscientifically to sub-divide the more conspicuously
sunshine-loving and day-flying flies into:—(1) flower and honey seeking
flies; (2) cattle pestering sweat-flies; (3) skin-piercing,
blood-sucking flies; (4) insectivorous flies; (5) fungus flies; (6)
carrion and filth flies; and to these must be added another small group
(7) which comprises those of the wondrous family of the _Œstridæ_, the
most horrible though not the most injurious of the animal persecuting
and torturing flies; this last group, strange to say, are absolutely
destitute of any mouth and feed only in the maggot stage. In many cases,
however, it happens that the males and the females differ in feeding
habits as well as in colours and markings, whilst only their patterns of
wing-veins and some less prominently apparent features are constant in
the two sexes. These circumstances discountenance the above grouping.

Again, if we tried to group our flies with adequate regard to their very
diverse habits of life, in the larval stage as well as to their
subsequent metamorphoses, we should find that these are details which
are obscure and in many cases unknown or imperfectly recorded. However,
after much study and many revisions, a scientific classification has
been contrived based upon the minutely differentiated characteristics
which are technically explained in the Appendix to this booklet.

Whilst the notorious house-frequenting flies above-mentioned and the
blue-bottle are remarkably omnivorous in their feeding, the great
majority of outdoor flies are quite otherwise inclined, and do not find
much attraction in anything but their own individual preferences.
Indeed, the breeze-flies, and many others, avoid human habitations; even
the grey blow-fly, unlike the blue-bottle, rather seems shy of the
house. In the above grouping, according to feeding habits, the house-fly
must be preferably consorted with (2) sweat-flies, but the blue-bottle
with (6) carrion flies; however, the house-fly and the blue-bottle are
very near akin, and by reason of similarity of wing-pattern both are
included in the family of the _Muscidæ_.

In the entomological systematist's classification the primary separation
of flies into two sub-divisions starts with a difficulty, for it is
based upon circumstances often obscure and in some cases at least
imperfectly known.

The first sub-division, _Diptera Orthorrhapha_, comprises those flies
which in the stage of the pupa or chrysalid disclose the outline of the
perfect insect; in the other sub-division, _Diptera Cyclorrhapha_, there
are grouped together all those flies of which the larvæ make for
themselves a puparium or barrel-like case out of their larval skin.

The first mentioned sub-division comprises all the gnats, midges, and
most of the slender flies which are outside the scope of the present
work, but it also includes a few kinds of more stoutly built flies, to
which some allusion will be made in the following pages, as for example,
the breeze-flies, _Tabanidæ_.

The second sub-division comprises many families, including the
_muscid-like_ flies, of which the house-fly is the type. The flies of
this type are to be found in the families of _Muscida_, _Anthomyida_,
_Tachinida_, and _Cordylurida_, comprising nearly 700 British species,
of which many rather closely resemble one another when superficially
observed.

The approved classification of flies is to some extent dependent upon
the formation of the antennæ, but the unique feature of the systematic
differentiation is based upon a very intricate method of scrutinising,
identifying, and numbering the vein-like strengthening ribs called
veins, nervures, or nerve-lines, which, starting from the shoulder, mark
with characteristic patterns the transparent tissue of the wing. We are
rather compelled to follow something like this plan (simplified) for the
purpose of clearly distinguishing the "lesser house-fly" from the common
"house-fly."

In the accompanying illustrations rather similar patterns of wings are
shown; these are typical of the _Muscidæ_ and _Anthomyidæ_, which, taken
together, comprise amongst others all the cattle and human pestering
"sweat-flies"; only a few really blood-sucking flies are included
amongst the _Muscidæ_.

In critically comparing these four patterns, the chief feature to be
observed is the small rib-like nervure called the "discal" "cross-vein,"
which is situate in the very middle of the wing, and which connects the
lowest of a group of longitudinal nerve-lines or veins in the front (or
upper) half of the wing to the uppermost of the other group of
longitudinal nerve-lines in the hind (or lower) half of the wing. Three
"main" longitudinal lines, technically termed "veins," are theoretically
recognised as constituting the upper group and four "main" longitudinal
lines the lower group; but these "veins" (numbered 1, 2, 3, 4, 5, 6 and
7) will be found to be varied in different families and genera, each
often with characteristic diverging branches, whilst some veins may be
rather inconspicuous or quite absent. We will here devote our attention
only to two such "veins," those respectively termed "vein 3" and "vein
4" which are connected in the very middle of the wing, as above
mentioned, by the small but always distinct "discal" "cross-vein." The
illustrated patterns herewith show wings divided into about twelve
compartments or cells, to all of which learned entomological writers
give troublesome technical names, not nearly so intelligible as the
nomenclature symbols of the late Rev. W. J. Wingate, explained in the
Appendix herewith. For present purposes a simple observation of the
(externomedial) vein "V, 4," where it is the lower boundary of the
(subapical) cell "O, 4^2," will suffice.

[Illustration: Fig. 3. Wing patterns contrasted.]

The pattern of the first figure illustrates the wing of the common
blue-bottle; here "vein 4" does not run at all straight in the last part
of its course, but curiously bends very suddenly upwards at an angle and
meets the margin very near to "vein 3." In the wing of a large
blue-bottle it will be easy to recognise this plan.

The pattern of the second figure is rather similar, for the vein 4
likewise has a sudden bend upwards; it terminates practically contiguous
with vein 3 at the margin. This pattern is characteristic of the
"house-fly"; thus it will be easy for the reader to identify the common
house-fly by the close resemblance of its wing pattern to that of the
blue-bottle, with which it is classified in the family of the _Muscidæ_.

In the pattern of the next figure the vein 4 runs comparatively straight
throughout and meets the margin at a spot intermediate between the third
and fifth veins; here all the main nerve-lines diverge more evenly and
terminate more equi-distantly apart; this latter plan is the wing
pattern which will suffice to identify the lesser house-fly, but it is
shared with all the _Anthomyidæ_, and more or less with some others,
which are very common outdoor flies.

The pattern of the lowest figure illustrates the wing of the common
blood-sucking stable-fly, _Stomoxys calcitrans_, which only occasionally
invades the house. Here the vein 4 is deflected upwards towards the
margin ending near the termination of the vein 3, but the bend is a
smoothly rounded curve and not a curiously abrupt angle, as in the first
and second figures.

If the reader will study the house-fly in captured specimens, he will be
able to observe that they slightly differ in their inconspicuous
colouration and markings.

The male of the lesser house-fly is sometimes more observable than the
male of the commoner house-fly, by reason of his being a most
indefatigable dancer with companions in mid air around any central
ornament, and also by reason of his possessing pale patches, more or
less yellowish grey, on the sides of the abdomen; but such markings are
also in some degree observable in other male flies, being very
conspicuously of a brighter yellow in the common small outdoor
raven-fly, _M. corvina_. The back of the thorax of the house-fly is
marked sometimes distinctly, sometimes indistinctly, with four dark
lines on an ash-grey background; the lesser house-fly has three faintly
darkish lines only. Quite a number of outdoor flies have similar
markings, but these often look like closely adjacent or indistinct
spots. The wing pattern is the readiest guide for distinguishing the
lesser house-fly, both male and female. The males of the hairy (almost
bristly) raven-fly also indulge in the dancing habit, but still more so
do those of the latrine-fly, _Fannia scalaris_, which may be
distinguished by its uniformly ashy-grey abdomen.

These common co-inhabitants of our dwellings vary in size according to
their nourishment when in the larval stage (maggots); after the perfect
insect emerges from the puparium, it swells out and fattens, but does
not grow in the real sense of the word. If 1000 house-flies will weigh
an ounce, then it may be calculated that 1600 average specimens of the
other kind will likewise weigh an ounce.

In representing that the house-fly exceeds the lesser house-fly in
numbers in the proportion of twenty or thirty to one, it must be borne
in mind that the occurrence of the latter varies widely—casually
according to the locality, and temporarily according to the time of the
year, being more commonly observed when and where the other kind is
scarce.

The lesser house-fly has summer broods at longer intervals than has the
common house-fly. Towards the end of the summer its last brood
hibernates in the puparium, and emerges as early as the end of March or
early in April, whilst the common house-fly is not usually observable
until a later date, although it is credited with more generally braving
the dangers of attempting to hibernate in the imago stage. My attempts
to test the capability of the house-fly by aiding October and November
flies to hibernate invariably terminated in the creature's death long
before springtime. However, it is very apparent that under the shelter
and encouragement of warm winter environments in towns, amidst
restaurants, bakeries, large hotels and certain factories, as well as
and even more than in mews, adult flies of the latest autumn broods can,
to some extent, survive mid-winter with very little or no prolonged
hibernation.




                              CHAPTER III

               SOME OTHER FLIES AND THEIR DIVERSE HABITS


Just as the common "house-fly" and the "lesser house-fly" are often in
error regarded as the same species with an insignificantly small
difference of size, so the identity of each in turn may be confused with
several other species which are not uncommon, but they are all normally
outdoor flies.

The chief of these is the excessively common stable-fly, _Stomoxys
calcitrans_, whose generic and specific designations are well given, for
they mean "sharp-mouth," "kicking," the latter word denoting the action
of the tormented horse; it has a long, thin, stiff, skin-piercing,
shining black trunk, furnished with two lancets. It is an eager blood
sucker. In size and colour it rather resembles the house-fly, but anyone
who is keen sighted will recognise it at once by its bayonet-like trunk,
held projecting prominently in front of its head. It is much addicted to
basking outdoors on sunny walls, but on the approach of darkness or of
inclement weather it will occasionally seek shelter indoors. Its wing
pattern rather resembles that of the common house-fly, as has been
previously explained.

Round about dairy farms _Hæmatobia stimulans_, a fly slightly smaller
than the stable-fly, with a striped thorax and a blood-sucking trunk,
will often leave the cattle to assail humanity. A still smaller,
somewhat hairy, muscid type of fly, _Lyperosia irritans_, is also a
common aggressor of oxen throughout the summer.

_Musca corvina_, the raven-fly, is smaller than the house-fly; it has
very distinct dark markings; the abdomen of the female is chequered, but
that of the male has a black central stripe on a yellowish abdomen. It
frequents gardens, parks, and meadows. It is much less prolific than the
house-fly, with which it shares the sweat-fly pestering habit.

_Cyrtoneura simplex_ is a little smaller and more common than the
species last mentioned; its larvæ are bred in the dung of cows and other
animals which it very severely pesters. However, many species of
dung-bred flies do not in the least participate in the cattle-pestering
habit.

The _Anthomyidæ_ are a family of about 250 small and medium sized garden
frequenting and country flies, mainly of flower and honey seeking
habits. Nevertheless, some are dung-frequenting; none are blood-sucking,
but several are cattle-pestering sweat-flies, which, even more
pertinaciously than the house-fly, will circle round one's head and
repeatedly buzz against one's face. Of these, the small _Hydrotœa
irritans_ and _Hy. dentipes_ are amongst the worst offenders. A few of
the _Anthomyidæ_ are vegetarian garden pests; the larvæ of the
cabbage-fly, the root-fly, the onion-fly and the celery-fly are, in some
seasons, very destructive. The so-called "turnip-fly" is a small striped
beetle of the same genus, _Phillotreta_, as the unstriped "flea-beetle"
of the hop-fields. The larvæ of the majority of the species of the
family of _Anthomyidæ_ are, more or less, feeders on decadent vegetable
matter, but some, like those of the genus _Fannia_, are preferentially
feeders on dung. The female of the latrine fly, _Fannia scalaris_, so
closely resembles the lesser house-fly that only the expert with a
magnifying glass, after a careful examination, can tell which is which;
the male differs from the male of the lesser house-fly by being without
the yellowish patches on the abdomen.

There is a larger and less common muscid fly, with an ashy-grey body,
but with reddish legs, named by entomologists _Muscina stabulans_, which
not only in body colour, but also in the pestering habit, resembles the
house-fly; its Latin specific name is rather objectionable as too
suggestive of the common "stable-fly," which name belongs to _Stomoxys
calcitrans_ above-mentioned; its larvæ have been found in cow-dung, but
they can also flourish on vegetarian fare.

The common blue-bottle is now named _Calliphora erythrocephala_
(red-head), and it can be recognised by its reddish face and black hairs
for a beard, whilst the less common blue-bottle, named _Calliphora
vomitoria_, may be said to have a reddish beard upon a black face; the
latter has the blue colour more evenly distributed over the abdomen,
whereon the former has dark markings.

_Polietes lardaria_ is a fly sometimes mistaken for the blue-bottle; its
specific name is rather too suggestive of resemblance in habit. It may
be recognised by its having four black stripes on the thorax, by its
large white squamæ, and its tesselated glaucous abdomen; its wing
pattern classifies it as belonging to the _Anthomyidæ_, whilst the true
blue-bottles belong to the _Muscidæ_, and the grey blow-flies to a
section (_Sarcophagina_) of the _Tachinidæ_.

There are some other outdoor flies which are not very dissimilar to the
common blue-bottle, but they are more soberly coloured, ranging from
bluish black to speckled and tinted greys; some of these have a pattern
on the shiny upper surface of the abdomen which is conspicuously and
beautifully chequered. Closely akin to these latter is the large grey
blow-fly, or flesh-fly, _Sarcophaga carnaria_; it is much referred to in
entomological books as of marvellous fecundity. The female deposits not
eggs in a few hundreds, but already hatched maggots to the number of
many thousands. Amongst half-a-dozen rarer kinds of smaller grey
blow-flies the females differ in their striped markings, but their
respective males seem quite indistinguishable apart.

Notwithstanding the prodigious fecundity of the grey blow-fly, the
credit of being a practically useful scavenger of carrion must be given
only to the blue-bottle, which is of a more robust habit, and which so
promptly monopolises available matter that _Sarcophaga carnaria_ and her
congeners are sometimes, perforce, compelled to give their larvæ a mere
vegetarian diet.

The yellow cow-dung fly, _Scatophaga stercoraria_, is inoffensive, and
one of the commonest flies observable in the course of a country-side
ramble. It and its congeners are distinct in habits and appearance from
any of the other flies above-mentioned. In this species the male is
larger than the rather more smooth and dull-coloured female. Its body is
furry but slender; it has small eyes and head parts. In repose it holds
its wings parallel close above the abdomen, more like the
"breeze-flies," or true "gad-flies," than the ordinary muscid flies.
Although its proboscis does not seem as formidable as that of more
insectivorous flies, yet it may sometimes be observed pouncing upon some
small fly, which it holds with its powerful legs. This fly does not
appear to be very predaceously inclined; perhaps it is only "acting a
part," like some other creatures, including the amorous male of the
common frog, which, failing to secure a more natural and complacent
"partner in the dance," will in springtime seize upon and very
persistently cling to an astonished carp.

Amongst many flies with bodies favoured with a brilliant metallic sheen,
several species of green-bottle flies (_Luciliæ_) are notorious. Of
these latter _L. Cæsar_ is the most common, but _L. Sericata_ is by far
the worst in England, not uncommonly laying eggs upon sheep; many are of
a brilliant golden green, but some vary towards a coppery green; all
have red eyes and silvery faces. In summer-time these flies seize every
opportunity of depositing their eggs upon any sores or skin wounds of
animals; their larvæ normally feed on carrion and dung. The
green-bottle, like the blue-bottle flies, are fond of both sweets and
filth, but they do not pester wholesome animals as do the sweat-flies.

Next to the _Muscidæ_ the most often observed and easily recognisable as
a distinct family of flies are the _Syrphidæ_, which include the
"hover-flies," the drone-flies (often mistaken for the male of the
hive-bee), and a number of other very common flies of a generally
similar full-bodied shape, in most of which colour stripes and bands
more or less suggest a comparison with wasps. The numerous species
native to Great Britain are widely distributed, and, excepting the rare
and very hairy _Merodon narcissi_, of which the larvæ feed on liliaceous
bulbs, none is injurious and some are beneficial. Nearly all the flies
of this family frequent flowers. The habit of many to hover for hours
about a favoured spot, as if for mere pleasure, is remarkable; but it is
not generally recognised that some of these hover-flies (of the genus
_Syrphus_) are hawking for winged aphides and other small insects, which
they quickly suck dry and drop whilst still on the wing. Many of the
flower-frequenting _Syrphidæ_ are great devourers of pollen; all have
strongly developed suctorial mouth parts.

The larvæ of the various syrphid flies differ greatly in appearance and
habit; some are terrestrial; some aquatic; some semi-aquatic; some feed
on decadent vegetation; some on sewage and filth, and some are
insectivorous. Most useful to the horticulturist are those of the genus
_Syrphus_, which feed on green-fly and other aphides. The most curious
in shape are the "rat-tail" maggots of the common drone-fly, _Eristalis
tenax_ (also others of allied genera), which can extend their long
tubular tails and breathe atmospheric air through the same whilst lying
under water. The larvæ of the genus _Volucella_ are found dwelling in
the nests of bumble-bees and wasps; it is rather uncertain how far they
are commensal, or parasitic, or devourers of dead matter. Some of the
syrphid flies are single-brooded, but some at least are double or
treble-brooded in the year; records are wanting about many, and which,
if any other than the common drone-fly, are multi-brooded. Anyhow, none
appears to breed in Great Britain as rapidly as do the house-fly, the
blue-bottle, and other muscid flies.

The larvæ of _Conops flavipes_ are parasitic in the body of the adult
bumble-bee, and they pupate therein.

The small family of the _Stratiomyidæ_ contains a few fairly common
species called soldier-flies; these are interesting as linking
_Orthorrhapha_ with _Cyclorrhapha_; their larvæ are some aquatic (the
star-tailed maggots), others terrestrial, and some have hard shell-like
skins; but they are not so curiously like a creeping marine limpet as
are those belonging to the genus _Microdon_ (of the _Syrphidæ_), which
are rare and wonderful dwellers in ants' nests.

There is a curiously shaped race of parasitic flies which cling to the
host like a louse, called _Hippoboscidæ_; these have more than the usual
provision of claws to their feet, both in the number (normally two) and
size of the claws. The forest or spider-fly attaches itself to some part
of the body out of reach of the horse's tongue. The ked, tick, or sheep
louse-fly has a similar mode of life, and, after selecting its host, it
becomes wingless. These flies, strange to say, nurse and nourish their
larvæ within the oviduct, and, when one might think that they were
laying their eggs, they are depositing pupæ or larvæ just ready to
pupate. There are some species of the family of the louse-flies which
infest birds.

The true gad-flies of the family of _Tabanida_ were, and sometimes still
are called "blinden breeze-flies," and sometimes dun-flies; by a very
easy mistake the countryman's word "blinden" (blind) has got changed by
authors in books to "blinding," which is nonsense, and misses a
wonderful instance of old-folk knowledge; the females are amongst the
most inveterate blood-sucking flies, but the males are mere idle
loiterers in summer sunshine on flowers; the eggs are laid on herbage in
moist situations; the maggots and pupæ of many of these species are said
"to be found in the soil," and some, if not all the larvæ, are
predaceous, attacking worms and underground larvæ of various insects.
They are more or less midsummer flies and are single-brooded. There are
several largeish species (of the genera _Tabanus_ and _Therioplectes_)
found in Great Britain, and they are diversely distributed, being
respectively woodland, moorland, lowland, and highland inhabitants. The
great ox-gad-fly is as large as a bumble-bee, though more long than
broad in body, but the term gad-fly is often wrongly given to the
worble-fly, which is really more bee-like, being furry and rounder in
body. The genus _Hæmatopota_ comprises three smaller sized extra vicious
blood suckers, _H. pluvialis_, rather common, _H. italica_, very local,
and _H. crassicornis_, darker in colour and with spotted and dark tinted
wings. Several of the large gad-flies have dull-tinted wings. They have
large, shallow, brightly shining and curiously banded compound eyes, but
no "ocelli"; they all seem to be at least semi-blind, and the females
are rather sluggish, except between the hours of 11 a.m. and 5 p.m. in
bright midsummer sunshine. The females hunt entirely by scent and are
easily captured when attacking human beings; they alight on their
victims with a stealthy silent approach. They appear unable to
discriminate between clothing and bare skin as suitable spots for
feeding. Amongst a band of mountaineering pedestrians, on a sunny day,
it was observable that there would be a dozen or more "blinden
breeze-flies" settling on the back of one, whilst the rest of the party
were only favoured now and then by one or two apiece. It was apparently
the smell of the "home-spun" coat which attracted; the colour of the
garment did not seem to be the cause of the selection. Sunshine loving
flies prefer white and pale colours. If a dog could speak, he would
explain the smell of some "finished" cloth, but, for the sake of the
fastidious, the secret is not here disclosed.

Very closely allied to the true breeze-flies in habit of life are the
species of the genus _Chrysops_, of which two only are often met with in
England, namely _Ch. cœcutiens_ and _Ch. relicta_; these flies are very
keen blood suckers; they are smaller, slightly more slender and brighter
coloured than the commoner _Tabanidæ_; it is characteristic of the genus
_Chrysops_ that the antennæ are quite twice the length of the remarkably
short horns of the majority of common full-bodied flies; all the species
possess beautiful golden glittering eyes (whence the name _Chrysops_),
and their wings are spotted and tinted.

One of the most horribly disgusting but serious facts connected with
flies is observable most conspicuously amongst the wondrous family of
the _Œstrida_. These pass the larval stage of life, not on, but inside
the bodies of living animals; and the perfect insect, strange to say, is
absolutely destitute of a mouth opening. Much misrepresentation has been
prevalent, based entirely upon surmise, connecting "myiasis" in mankind,
which is various but very rare, with the common infliction of horses and
horned cattle with _Œstrid_ maggots. Myiasis is the medical term given
to all the various forms of animal infliction by internal parasitic
maggots, and this subject is reserved for discussion in the next
chapter.

The characteristics and natures of the very numerous tribes and families
of other kinds of flies will be found summarised in the Appendix of this
booklet.




                               CHAPTER IV

                       MYIASIS AND THE _ŒSTRIDÆ_


The family of the _Œstridæ_ is the most curious and horrific of all the
different tribes of flies; it is very limited in species, of which five
or six are prevalent throughout Great Britain. The worst of these could
be almost exterminated with ease, but unfortunately mistaken ideas have
prevailed, and graziers commonly believe that though the sheep's nostril
fly is conspicuously harmful and dangerous, the horse's bot-fly and its
congeners are negligible as regards the practical health of the host.
The bot-fly and the worble-flies are all of a largish size, only the
sheep's nostril fly and _Œstrus hæmorrhoidalis_, which latter infests
the throat and rectum of the horse, are of a medium size.

It has been known from very ancient times that man himself was not
exempt from some fly, which was imagined to resemble the horse's
bot-fly, and it has been wrongly surmised that many different creatures
and all ruminant animals were more or less subject to the attacks, each
one of its own kind, of œstrid fly. It is undeniable that man is
sometimes internally afflicted with dipterid larvæ, but it is most
certain that the fly to be incriminated is not a congener of the horse's
bot-fly.

An old illustrated French encyclopædic work gives coloured pictures of
the flies and larvæ of _Œstrus bovis_ (the worble-fly of the ox) and of
_Œstrus equi_ (the bot-fly of the horse), but only the larvæ of a
so-called _Œstrus hominis_ is figured. Recently, however, new attempts
have been made to identify the species causing intestinal myiasis, of
which the larvæ are observable from time to time in the course of
post-mortem examinations and during anatomical study. Of recent years it
has been suggested that the lesser house-fly is addicted to such a
manner of breeding; then later that another species of the same genus
has been found to be the real culprit. However, the peculiar larvæ of
these last-mentioned flies do not in the least resemble the fat round
larvæ of the true bot-fly or of the worble-fly, which are correctly
represented in the above-mentioned French work, nor the round and rather
smooth maggots which were observed in Westminster Hospital nearly fifty
years ago, and at other places from time to time both before and since,
giving rise to much wonder and discussion, and also to very incredible
tales.

Another more credible surmise attributes the offence of human intestinal
myiasis to _Muscina stabulans_; if this be correct, the infliction would
be probably due to the subject having eaten damaged and egg-laden plums
or similar fruit, for _M. stabulans_ is credited with being normally,
though not exclusively, fruitarian or vegetarian.

If any one of the above suppositions be true, it does not exclude any
other one, amongst many explanatory surmises, from being possible.
Judging from the remarkable attractiveness of the odour of humanity to
the common house-fly, and from the fact of the maggots possessing well
developed tenter-hooks on their heads (somewhat like those which the
bot-fly maggots use for internal attachment), it is just as likely, nay
more likely, that this species (as the writer stated for the information
of the authorities of Westminster Hospital nearly fifty years ago) is
more than any other capable of adopting such a life-cycle existence;
these maggots would mature after five or six days feeding and then
emerge. If there were a veritable "_Œstrus hominis_," however rare, the
hairy and peculiar female would be conspicuously observable, a
persistent hoverer about the person of her victim until she had attached
eggs to his body, from which the maggots would not emerge until after
nine months. Most of the tropical flies, which are said to similarly
attack humanity, may be rather compared to the green-bottle flies which
infest sheep, but the latest medical records and reports profess to
identify ten or twelve species of very different genera as having
myiasic capabilities.

The family of _Œstrida_ has been fitly divided into three sections,
namely, the _Gastrophilinæ_ (the larvæ living in the gullet, the
stomach, or the intestines), the _Hypoderminæ_ (worble-flies), and the
_Œstrinæ_ (nasal or nostril flies); all the species are hairy or furry,
and the gravid females fly slowly with loud buzzing, in a characteristic
attitude peculiar by the bending downwards of abdomen and tail, with a
much extruded ovipositor.

The sheep's nostril-fly, _Œstrus ovis_, has a chequered abdomen and is
less hairy than others; it is the type of the section to which the
generic term _Cephalomyia_ is given in some books; species of this
section attack deer and other animals.

The section termed _Hypoderminæ_ comprises the "worble" flies or
"marble" flies. One may imagine that the latter name indicates in the
mind of the cowherd the appearance of the round pustulent boils on the
hide of the suffering animal, and that the former name is a corruption
of "worm-hole," originating with the tanner, observant of the
deterioration of injured hides. A mixing of the terms worm-hole and
marble probably originated the name "warble." The maggots live under the
skin on the back of oxen, and breathe externally through openings in the
boil-like excrescences. The discoloured flesh of infected oxen is called
"flecked." Two species of worble-flies are prevalent, one or the other,
in many parts of England.

The third section, to which the sub-family termed _Gastrophilina_ is
sometimes applied, comprises the "bot-fly," which commonly infects the
horse; it is the imperfect knowledge of this latter which has led to
erroneous surmises explanatory of the horribly disgusting fact of human
intestinal myiasis.

All the species of all the three sections are single-brooded. Although
the flies themselves can inflict no immediate pain, at their mere sight
all the animals out at grass on the farm are seized with an instinctive
terror, conspicuously greater than when attacked and copiously bled by
any "blinden" breeze flies, which, however, fly more silently and settle
on their victims very furtively. One can understand the violent efforts
of the horse to free himself from the exceedingly painful bites of a
newly attached forest-fly, but one can only wonder at the frantic
galloping of oxen and horses to and fro when a non-biting œstrid fly
buzzes about like a harmless fat bumble bee and slowly approaches.

The females of all the worble-flies, the nostril-flies, and the bot-fly
are short-lived, appearing on the wing in August, possibly seen a few
days earlier. In the act of ovipositing they make themselves very
conspicuous; they lay their eggs whilst hovering in the air, their
extruded ovipositors attaching glutinous eggs to their victims. The
hatching of the eggs of the bot-fly is assisted by the habit of animals
to lick themselves and each other, when certainly their warm, moist
tongues will convey into their mouths the newly emerged bot-fly's
maggots, which many months later are to be found attached to the
internal lining of the unwilling host's stomach. When fully grown in
June, these maggots loosen their hold, are discharged with the dung, and
pupate in the soil.

No satisfactory account has yet been given as to the early stages of the
maggots of the worble-flies. The eggs, having been attached to hairs on
the host's hide in August, the prominent round pustulent swellings,
called worbles, wherein the maggots dwell, do not become conspicuous
until the following months of April and May. It is a reasonable surmise
that the obscure and long first-period of the maggot's existence may
more or less conform to that of some of those flies which are also
single-brooded but are predaceous or parasitic on insects. The newly
hatched maggot perhaps can crawl, but does not feed until after several
moults; at each moulting the strange creature becomes smaller and
smaller, but probably at the same time is provided with a new head well
suited for the purpose of that period; firstly, with a burrowing or
grappling head, and in due time with a feeding suctorial mouth, and then
only does practical growth begin. No dipterid flies, at all events,
known to be native to Great Britain, possess skin-piercing ovipositors.

I have been astonished to read in current literature much about œstrid
flies which is not in agreement with my long course of personal
observation; for instance, one high authority (F. R. S.) writes that
œstrid "_flies_" appear from May until October, and hints that their
egg-laying aggressions upon their victims are not conspicuously
observable. I feel confident that the facts are quite otherwise.

That the bot-flies normally (and a few others abnormally, but for short
periods only) pass a very long larval stage in the stomach and
alimentary canal of herbivorous animals is one of the greatest marvels
of insect life. All other growing creatures, which normally breathe in
free air, require a certain large amount of breathable oxygen; and they
would be stupefied or killed by a much smaller percentage of carbonic
dioxide and other fermentive gases of digestion than undoubtedly exist
in the strange abode wherein the bot-fly maggots dwell during the entire
period of their feeding career. It has been stated that fly maggots
artificially ingested into the human system have emerged alive in a
normal condition, but the repulsive and objectionable experiment is not
stated to have procured well nourished and full grown normally pupating
larvæ. Some of the maggots of human intestinal myiasis are not perhaps
amenable to artificial culture up to the stage of final metamorphosis;
and they do not appear to have developed a breed or new species with a
distinct habit of life. All the credible accounts of human intestinal
myiasis point towards some fly which is plural-brooded, and of which the
larvæ develop rapidly and promptly quit the body all at once; otherwise
more than one infection must have occurred. The tales of prolonged
continuous breeding, with slow and prodigiously copious emergings at
intervals, should be altogether discredited.

It is an amply warranted criticism to say that recently published
records by authorities, in an endeavour to comprise every reported
instance of myiasic infection, seem to countenance mere coarse
Gargantuan jokes. On the other hand, it is painful to read such a
"cock-and-bull" story as that of the doctor about his elderly lady
patient, up whose nostril a gravid female blue-bottle flew and
successfully performed the prolonged and delicate operation of laying
therein a large batch of eggs, in spite of all attempts to expel the
invader by violent sneezing. Day by day the said doctor observed the
terrible injury, and the symptoms accompanying the growth of the feeding
maggots, whilst the injection of a spoonful of paraffin would have
effected an instantaneous cure.




                               CHAPTER V

                          GENERAL LIFE HISTORY


Whereas the blue-bottle rarely enters the dwellings of mankind, except
gravid females led by the sense of smell in search of fish, or flesh
meat, and (less eagerly) sweets, both species of house-fly and _both
sexes_ seem to delight in the mere odour of humanity; breeding females
will seek the larder and the dust-bin, but others will very provokingly
pervade all quarters. Although avoiding a dark or deeply shaded room,
the house-fly seems to like partial shade; it will be content to remain
indoors and to rejoice in a warm kitchen, even on a hot summer's day,
whilst all the other kinds of flies are enjoying the outdoor sunshine.
It may be said of nearly a dozen other species, occasionally observable
crawling on window panes, that they are "outdoor" flies, and that their
occurrence indoors is accidental. In fact, they are mostly observed when
trying to escape.

Next after human habitations, stables, cow-sheds and pig-sties are the
delight of the breeding female house-fly. Round about and in these
latter resorts she associates with an immense host of rather small sized
flies, and amongst a few others of equal size with the skin-piercing and
blood-sucking stable-fly; but many stablemen are ignorant of the
difference of the two kinds of flies and of the serious suffering of
their horses from the bites of the stable-fly. This lamentable ignorance
was shared by the joint authors of "Humble Creatures," published in
1858, when Neo-Darwinism was in vogue, and many books were published for
popularising a knowledge of common things and spreading an interest in
nature-study; this publication, which is still (1914) in print and very
little revised, has probably led some later would-be nature-study
teachers to follow suit in confusing the characteristics of the two
species. Very often the fly most numerously breeding in the manure heaps
of the mews will be _Borborus equinus_, or some other of the same
family, which are characterised by a very simple pattern of wing
nervures and by the absence of squamæ or scales behind the wings; also
the ankle joints of the feet are most peculiarly short and broad. _B.
equinus_, and a great host of other dung breeding flies of a still
smaller size, may be considered beneficial insects; they do not pester
cattle, and their larvæ make food more scarce for injurious flies.

The breeding habits of the blue-bottle are very conspicuous by reason of
its haste and boldness in taking possession of dead animals. It is
incapable of breeding in horse or cow dung, to which latter the
green-bottle fly often resorts.

The blue-bottle deposits her eggs, 500 or 600, preferably on dead fish,
or flesh, and sometimes on the sores or the flesh of wounded animals,
but both the house-flies preferably affect dung, carrion, garbage, and
all kinds of fermenting vegetable matter. It has been commonly but not
truly said that the principal breeding places of the house-fly are the
mews and the farmyards where manure is allowed to accumulate; the
house-fly has a preference for horse dung before cow dung, which is
preferred by some other kinds of flies; however, near towns, the
domestic dust-bins, heaps of market garbage, and deposits of town refuse
give rise to a worse plague of house-flies than stables. All these flies
deposit batches of white eggs, and are careful to place them as much as
possible in crevices and shielded from exposure to strong light, or from
draughts.

The two house-flies and the blue-bottle have similar larval stages, but
their larvæ, called maggots, differ. The larvæ avoid daylight and cannot
withstand dryness. As the larvæ feed, they have the power of ejecting or
excreting a juice, which dissolves the food before they imbibe the
material; their mouths are suctorial and are destitute of teeth or
biting jaws.

The larva of the house-fly is an eyeless and legless maggot, one half
inch long when full grown and extended; twelve cylindrical segments may
be counted in its body, or even thirteen if we separately distinguish
the small head segment, which may be withdrawn, and but little
observable; five or six rear segments are of nearly equal stoutness when
only half grown; afterwards counting from the three stoutish rear
segments, the others taper towards the very small head. The middle and
rear segments have pad-like bristly processes underneath, which aid the
maggots in creeping, in which action they also make much use of the head
segment's grappling hook. The maggots feed voraciously, but they seem,
like the larvæ of the honey bee, to pass out very little anal excreta;
some have thought that, like what is said of bee larvæ, no excrement is
discharged until after the imago has emerged from the puparium; but such
conduct seems altogether incredible. In the bee-hive doubtless the
assiduous workers ever wash their babies clean and lick up all matter,
just like domestic cats and dogs, when nursing their young.

The larva of the blue-bottle, called a gentle, is proportionately larger
but very similar, except that the rear segment possesses a ring of
tubercles, which may have some useful function in connection with two
breathing tracks, which have their orifices at that part of the body.

The larva of the lesser house-fly is very peculiar; all its segments
have projecting tubercles; its whole body is rather louse-shaped, having
not cylindrical but somewhat flattened segments, of which the middle are
the broader, and those near the head and tail the narrower.

The transformations in the case of the blue-bottle are typical of the
house-fly and others of closely related families and genera which are
many-brooded within the year; these creatures develop very rapidly
immediately after emerging from the egg. Some other kinds of dipterid
maggots, which are single-brooded, pass a very prolonged and obscure
early period of skin-shedding and non-feeding, a preparatory sort of
baby-hood metamorphosis; then at last they begin to feed voraciously and
to follow the general habits of other maggots. Some maggots curiously
refuse to feed except in company; probably some are unable to feed on
dung except where other species are providing the necessary dissolving
juice.

When the common maggots or gentles have ceased feeding, they burrow into
the ground or crawl away, often to a considerable distance, apparently
seeking a secluded, a more wholesomely clean, and a dryer spot. During
this migrating time, they are palatable food for many birds, which would
not eat them in their former food-loaded or unscoured state. Indeed, it
is doubtful whether either a vulture or a raven could eat a fly-blown
carcase without danger of myiasic punishment. The skin of the larva
whilst growing is transparent, but, when about to pupate, it thickens
and becomes an opaque creamy white.

The most marvellous part of the metamorphosis of the blue-bottle is
concealed, when the gentle becomes the pupa; according to Réaumur the
embryonic fly develops most curiously inside the puparium by a procedure
not exactly like the change from the caterpillar to the chrysalid in the
case of the butterfly. After a pause of a day or two, the front segments
of the fully fed maggot contract, so that the body assumes a barrel-like
shape; the skin then hardens, and turning a reddish brown it becomes a
much contracted shell or case called the puparium. However, the long
slender maggot has done something more than merely shrink and shape
itself conformably to the case; it has withdrawn its embryonic head, so
small as to be hardly distinguishable microscopically, together with its
embryonic legs, wings and thorax into its embryonic abdomen! As the
development proceeds, and the embryonic members of the future perfect
insect acquire their destined shape, the immensely increased head and
the thorax with its appendage members slowly emerge, and the partly
inverted integument of the abdomen rolls back, disclosing the shape of a
fly not before recognisable.

Other naturalists would have it believed that the true account of the
transformation is as follows,—when the maggot has shrunk and freed its
body inside its skin which forms the case or puparium, all its
pre-existing internal organs become absolutely dissolved; then out of
the fluid mass a new growth ensues, constituting the pupa with its
recognised shape. This account is the one represented in most modern
entomological books, and is based partly upon B. T. Lowne's monographic
work on the blow-fly.

The comparative embryologist of our day is inclined to be a
hyper-theorist, and so it seems that some have not remained content with
either of the above accounts; to them, apparently, the production of the
large and complex head of the imago out of a single small anterior
segment of the maggot requires a more recondite explanation, and must be
brought into harmony with analogous facts. To this end some degree of
linked support is found by the investigations of microscopic anatomy,
and it has been conjectured that not one or two head segments, but five
are lying blended and embryonically hidden in the larvæ, all ready to
bud forth. However, for fear of wearying too much with the theories of
advanced erudite scientists, the following _jeu d'esprit_ is presented,
instead of a more elaborate and sober attempt, to lure the unscientific
lay reader to an extreme hypothetical conception of the "essential
unity" underlying the apparent diversities of Nature within that vast
domain of the Kingdom of Fauna, which is obviously outside the later
creation of a vertebrate Animalia.

[Illustration:

  Fig. 5. Illustrating the debatable continuity of a
  12-segmented structure throughout the metamorphosis.
]

The futurist's dogmatic CREDO of creative progress, "For him who would
meritoriously pass his histological examinations, and qualify as a
Professor and Doctor of Science, above all it is necessary that he
should acknowledge the unicellularity of the primæval OVUM (or egg),
whence proceeds the seventeen-segmented boneless ANNELID (or worm), out
of which there develops the quadrangular articulated crustacean INSTAR
(or shell-encased aurelian), which metamorphosises into the winged IMAGO
(the angelic? or diabolic? fly); in the contemplation of this knowledge
alone is there supreme Darwinian Modernismal salvation and felicity."
Amen.

In view of the prosaic illustration of transmutation, figure 5 above,
the futurist disciple will have to accept the seventeenness of
segmentation by something like faith without sight.

The quadrangularity of the crustacean stage is based upon the idea that
the wings bud out from the two upper corners, whilst the legs develop
from the lower corners of the transmuting instar.

Perchance the reader will desire information about the use of this
curious word "instar," which has not the honour of notice in Dr. Sir J.
Murray's New English Dictionary. One might well feel proud of the
opportunity of adding the smallest item to such a stupendous and
monumental work, but I fear I am only qualified to venture a fair guess.
Virgil, I believe, used this term in allusion to the legendary wooden
horse of the Greeks at their siege of Troy. Some time less than one
hundred years ago entomologists recognised that the words aurelian,
chrysalis, and pupa were none of them an inherently fit term of general
application to the stage of insect life to be indicated. After many
attempts, this latest proposed substitute seems to be gaining favour.

The fly emerges after bursting apart the first four segments of the
puparium; this it does by a curious provision, whereby it can inflate a
chamber in its head in a queer, balloon-like fashion, making a bag-like
extrusion, which it uses as a punching and pushing machine.

After emerging from the ground, the fly withdraws the bag-like extrusion
and cleans itself. Its body soon grows fit and it becomes very active,
as long as daylight and warm weather favour it; otherwise it seeks
shelter and becomes quiescent; however, artificial light and heat will
awaken it to nocturnal activity. Sweets, carrion, and filth are all
attractive to the blue-bottle, but the house-fly and the lesser
house-fly also find extraordinary attraction in both man and his
dwelling.

Considering the superfluity of other flies, and the multitude of other
insects ever ready to do duty as devourers of carrion, garbage, and
filth, the scavenging services of the larvæ of the house-fly can be well
dispensed with.

In civilised communities cremation in a refuse destructor is the only
sanitary method of treating town refuse. The economic value of the fly
is very little, and consists merely in its food value for certain birds.

In warm weather the scavenging capabilities of all the carrion and filth
feeding maggots are very remarkable, and there appears no exaggeration
in the statement by Linnæus, that the progeny of three flesh flies can
eat up the carcase of a horse sooner than it could be devoured by a
lion.

When a batch of eggs has matured in the abdomen of the female, she is
most careful in the location and manner of their disposal. Guided by the
sense of smell, she will not lay her eggs except in contact with food,
or in places securing her progeny access to their intended food. By the
use of her soft, slender ovipositor, which is telescopically extensile
and flexible, the eggs are deposited in shaded and concealed situations.

The house-fly is credited with laying batches of eggs at intervals,
perhaps four or more times, and about 150 on the first occasion, then
100, and less on subsequent occasions. Under favourable circumstances
the eggs may hatch within a few hours of their being laid. The maggots
of midsummer broods may be full grown and pupate in six days, and the
perfect insect may emerge from the puparium in another ten days of warm
weather, but in cold weather the pupæ of autumnal broods may remain
dormant for several weeks, or even months. When nine or ten days old the
mature fly may begin to lay eggs; hence, with such a life-cycle, in a
month of very favourable weather the progeny of a single pair may
number, say, 500; in two months' time the number may become 250 times
500; and in three months' time many millions!




                               CHAPTER VI

                     THE STRUCTURE OF THE HOUSE-FLY


The house-fly has quite the typical insect form, inasmuch as there are
three well defined sections of body—the head, the chest or thorax, and
the abdomen; also it has three pairs of legs, each with nine joints, of
which five joints constitute what may be called the foot. The twelve
segments of the maggot are observable as twelve rings in the puparium,
but in the fly the three which form the thorax look like one, whilst the
eight which should theoretically exist in the abdomen look like four or
five, until the rings of the ovipositor are counted.

The illustration on page 39 will make plain how the permanence of the
twelve-segment structure (conspicuous in the larval stage) has been
thought to persist throughout the life-cycle, but at the same time will
disclose how great is the change in the relative proportions of these
segments.

The prominent features of the hemispherical head are the two large
compound eyes and the proboscis or trunk-like mouth. The antennæ or
horns are very short appendages with three joints; small plume-like
projections, called arista, are attached to the third segment; the horns
hang down over a hollow in the middle of the face, and are insignificant
in size when compared with those of other kinds of insects; but their
structure viewed under the microscope is intricate, and they may be
efficient organs of sense perception, probably in part auditory. The
really unique feature is the retractile and suctorial proboscis, which
is often incorrectly regarded as the tongue; it is normally held doubled
up and withdrawn towards a hollow under the head, whence it is from time
to time extruded. The structure of this member is characteristic of the
entire tribe to which the house-fly belongs; it is a fusion or
combination of mouth parts, which in other insects are used more or less
separately for the various functions of inspecting, biting, masticating,
drinking and swallowing. In the house-fly the proboscis is absolutely
suctorial, and is not provided with the lancets used by the
blood-sucking flies for piercing the skin. Two maxillary palpi are
attached to the upper or basal part of the proboscis, which is called
the rostrum (a snout); the lower part is called the haustellum (a pump),
and it has at the end a pair of soft cushion-like lobes or lips, which,
when spread apart, form a heart-shaped pad with an opening in the
centre. The maxillary palpi are used for feeling and probably smelling.
Each mouth-lobe has a main collecting central channel and thirty
subsidiary cross channels of a wonderfully complex character. Imbibed
fluids pass from the mouth-lobes to the gullet along a passage in the
haustellum and the rostrum.

As with many other flies and other insects, there are on the top of the
head very small simple and rather inconspicuous eyes called ocelli,
three in number, between the large and prominent compound eyes, which
latter are said to possess each four thousand facets. The compound eyes
of the male fly are proportionately larger than those of the female; it
is quite observable that they approach each other more closely at the
top of the head, a feature of sex differentiation which is shared with
bees, wasps, and many other insect creatures. It is thought that a
single brain image arises from the combined views of the four thousand
facets of the compound eyes blending with the view conveyed through the
"ocelli." However, it is a most curious fact that it is the
inconspicuous ocelli which are of supreme importance visually. The
compound eyes have doubtless some special function, but throughout the
insect world the size of compound eyes is not a certain indication of
keenness of sight. The vision of the fly is good for distinguishing the
movement of any broad mass, but it is rather ineffective for observing a
thin line, as may be proved by slowly lowering a knife blade, with a
steady hand, when its body may be severed before the fly takes alarm. It
is a remarkable fact that the family of _Tabanida_ (blood-sucking breeze
flies), which are destitute of "ocelli," are the dullest sighted of all
flies; in fact, at least semi-blind. Moses Harris observed that a
blue-bottle became practically blindfolded when its ocelli were covered
with an opaque pigment. Probably this is the case with other insects.
Bees, which require long distance sight for home returning, are well
provided with ocelli. Butterflies, however, without the use of ocelli
have a distinct faculty of daylight vision for a moderate distance. The
investigation of sight by blindfolding is very difficult in flies.

There are two cephalic ganglions, which are regarded as the brain; these
are situated in the upper part of the head close to the neck. There are
also ganglions in the thorax with connections extending into the
abdomen.

The thorax is mainly occupied with the powerful muscles which actuate
the attached wings, the legs, and the small appendages called halteres
or balancers, which are supposed to be obsolete hind wings. There are
three unequal segments in the thorax; the pair of front legs belong to
the first segment, the wings and the pair of middle legs are attached to
the second larger segment, whilst the third is connected with the hind
legs and the halteres.

The breathing apparatus of the fly is distributed in portions over the
head, thorax, and abdomen; it consists of a number of internal air-sacks
with membranous ducts ramifying everywhere; the largest air-sacks are in
the abdomen near the waist. There is a pair of external spiracles to
each segment of the body, and these lead to the air-sacks.

The lines on the wings of the house-fly called nervures have already
been alluded to in Chapter II. These nervures are strengthening ribs to
the transparent tissues of the wings. The tissues are double (top and
bottom) enclosing the nervures, which are so united to the connections
called trachæ of the air-sacks, that the newly emerged fly helps to
extend its limp and crumpled wings by a process of inflating the
nervures.

The stomach is located partly in the thorax and partly in the abdomen. A
passage from the gullet passes through the neck into the lower part of
the thorax, where are the entrances to two long capacious chambers, of
which the upper one is the true stomach and the lower one a store pouch,
which latter may be likened to the honey bag of the bee. The fly
habitually regurgitates liquid food stored in this pouch, and, somewhat
after the manner of the cow chewing the cud, passes the same back into
the true stomach, whence it proceeds onwards through the digestive
track.

The abdomen holds all the other ordinary internal organs including that
which may be called the heart, and which lies above the stomach; it
consists of a long muscular tubular vessel with four contractile
chambers.

Although the organ called the brain is located in the head, and although
that called the heart is in the abdomen, yet some sense of control over
bodily motions curiously exists separately in the ganglions of different
parts of the body. This fact seems to make it possible for one extremity
of the body to continue performing a pleasurable action (say, the head
drinking honey) after the other extremity has endured a painful
catastrophe (say, amputation of the abdomen). However, it may be fairly
surmised that no creatures of a lower grade than warm-blooded vertebrate
animals feel pleasure and pain in any way at least after the manner of
mankind.

The most vital part of the fly is not the head but the thorax. A severe
squeeze on the thorax will effectually paralyse and kill the creature.
Muscular movements of different parts of the fly's body, which continue
after severance or other fatal injury, cannot be regarded as visible
proof of a slow death and prolonged sensibility.

Possessed of six legs, each with nine joints, the fly exercises a unique
capability of walking; the legs are moved three at a time, a front and a
hind leg on one side advancing simultaneously with the middle leg on the
other side; thus the fly proceeds most securely always poised on three
feet, which are so well furnished with pads, claw-like hooks, and hairs,
that it can walk over polished glass and can even walk upside-down along
comparatively smooth surfaces.

In comparison with the more heavily constructed wasp, with its four
wings, the house-fly, with its two wings, is the more alert and active
flier. The wasp is more robust than the fly and will be active in
weather too inclement for the latter; however, some of the frail and
slender gnats will brave cold temperatures impossible for the wasp.




                              CHAPTER VII

                DISTRIBUTION AND CONCENTRATION OF FLIES


It might be supposed that a strongly developed house haunting proclivity
would not be consistent with a disposition to roam far afield from the
locality of birth. Many clever experiments have been made with marked
flies released and recaptured within measured distances and times. After
an immensity of pains taken, very little profitable knowledge has been
arrived at thereby. Little of what we really want to know is indicated
by such a fact as that, out of hundreds or of thousands of marked flies
released, one per cent was recaptured at spots as remote as a mile
within two or three days, or by such a fact as that a large percentage
should be observed to remain within a more limited home circuit. The
variable factors of temperature, wind, sunshine and rain inevitably tend
to discredit the reliability of the observed results following any such
experiments.

Close observations of the habits of the house-fly reveal the very
appurtenant fact that the movements of newly-hatched flies, for their
first six or seven days' active life, differ from those of a more mature
age, when the breeding instinct has grown strong. The latter are
disposed to locate themselves for the rest of their lives in and about
one attractive spot, and they are indisposed to fly high above ground or
to travel far, unless it be with the object of leaving an unsatisfying
locality and discovering a better place. However, the younger flies seem
to feel no such restrictive influence, for, as soon as they have become
fit and the weather suits, they show an inclination to fly high and thus
may travel to very remote places. It is just the same with peacock, red
admiral, and tortoise-shell butterflies, which I have often reared and
released for adding to the interest and beauty of a flower garden. In
sunny weather many or most will soon wander never to return; those which
have remained a few days continue residence close round about,
especially if nettles, the food plant, grow in the neighbourhood.

It would be of great interest if we could discover how far a plague of
flies arising from unsanitory surroundings in one locality is liable to
spread to the injury of other localities.

On this subject nothing useful can be said other than can be safely
surmised from the known habits of the fly. The female has none of the
attachment of the honey-bee to its hive and community; she is not moved
by an instinct like that of the wandering bumble-bee in spring to found
a colony; she is indeed very solicitous about the disposal of her eggs,
but she is not impelled by any desire to place successive deposits in
one locality.

The lesser house-fly has proclivities similar to those of the common
house-fly, but probably she travels less far afield although a little
more inclined to outdoor life.

Very little is known about most of the common outdoor sweat-flies. Some
breed in dung, and may be many-brooded and otherwise resemble the
house-fly in prolific increase; others are more consistently vegetarian
in the larval stage and slower in development; and some are possibly
even single-brooded, like certain foreign large sized flies which
fortunately appear only for a few weeks of summer weather, for they have
a curious semi-blood-sucking habit of feeding after or alongside the
skin-piercing flies, and their suctorial mouths are capable of further
inflaming wounds and carrying infection from one animal to another.

The robust blue-bottle very closely resembles the house-fly in an
inclination to spread the brood. Mature females, however, do sometimes
show a slight temporary kind of "homing" instinct; having secured a cosy
corner and a well sheltered retreat in a sunny wall, the occupant will
battle for its possession, buffeting new comers.

Some of the smaller filth flies and many of the fungus flies have their
lives, in the imago stage, influenced and shortened by their extra early
sexual maturity; the females are fertilised whilst newly hatched and
their wings limp and unfolded. This fact accounts for our seldom seeing
some kinds of these flies abroad except females; and these are never
seen to indulge in dances, flirtations, and games of chasing and
buffeting each other, after the manner of so many kinds of flies. They
habitually fly low; nevertheless they travel very great distances, for,
though short, their flights are incessant when searching for their
special kind of food.

The most disinclined to roam of all common flies is the stable-fly. None
other is a more eager seeker of sunshine, but when basking on a sunny
wall it seems unwary and sluggish; it is seldom to be seen far from
where horses or cattle are stationed or stabled; however, it will make
very long journeys hovering about a driven horse or reposing on the car.

A plague of flies of local origin will not take many weeks of summer
weather to spread, but it is generally observable that plagues of flies,
like many other occurrences, are simultaneous co-incidences distributed
over wide areas and at places remote from each other.




                              CHAPTER VIII

                     NATURAL ENEMIES AND PARASITES


Flies, which are such insidious and pertinacious persecutors of man and
beast, are themselves the prey of innumerable enemies; many species are
much sought for by birds, they are devoured by lizards and toads, and
they are equally preyed upon by predaceous insects. Those flies which
have bodies with banded colours, and which otherwise somewhat resemble
bees and wasps, probably escape being the victims of some birds; but the
tribe of flies does not, like the beetles, the lepidopteræ, and some
other insects, furnish instances of other common protective devices,
such as bearing and voiding offensive secretions, or attempted
concealment in repose by mimicry of environment.

All insectivorous birds are fond of a diet of flies, and we may largely
attribute the spring-time immigration of the beautiful swallow tribe to
the fact that in the northern parts of the temperate zone swarms of soft
bodied dipterous insects abound, and there replace the hard cased and
more chitonous insects of hotter countries. The true swallow, the house
martin, and the sand martin, all require a special food for their
nestlings; and they also then require the longer summer days and the
prolonged twilight of our northern clime for the frequent feeding of
their young. The prevalence of flies near houses partly accounts for the
partiality of the swallow for nesting under the eaves of our dwellings,
where unfortunately the aggressive, the pampered, and the demoralised
sparrow in towns generally prevents successful breeding by appropriating
its nest and sometimes by eating its eggs. People who desire to favour
the breeding of the swallow should destroy the nests immediately after
the migratory departure of the builders. Their retention until the
following spring is in no way an enticement for rehabitation; on the
contrary, it favours the objectionable habit of the sparrow to use them
for a night resort, whereby they become very foul with bird vermin. The
cleanly swallow annually desires a newly built habitation, and a bare
peg projecting two inches from the house-wall will much encourage
swallows to start the foundations of a nest thereon.

Ground feeding birds of many kinds eagerly search for flies, their pupæ,
and their larvæ; even some finches will add flies to their diet in the
nesting season. Chaffinches are very fond of the house-fly at all times.

The wasps are assiduous hunters of flies, and, though possessing less
agility than their prey, they manage to pounce upon many victims. Very
common enemies are the predaceous _Empidæ_, of which numerous species
are native to Great Britain. Less common, but very observable when met
with, are the closely related robber-flies, _Asilidæ_, which are hardly
ever to be seen on a hot midsummer day without a captured fly held
between their strong front legs. The largest of the robber-flies, _A.
crabroniformis_, is a conspicuously fine insect. It equals the hornet in
length, but is more slender in body, tapering throughout the abdomen
towards the tail; it resembles the queen hornet in colour. The
dragon-flies also eat flies, but they mostly feed upon winged aphides,
gnats, and the like small game.

More secret destroyers of the fly brood are a few rather obscure
creatures akin in their nature to the ichneumon flies, which are
parasitic mainly but not exclusively on _lepidopteræ_. Likewise, certain
insectivorous beetles share in the good work of fly destruction.

Flies are often observable encumbered with minute vermin; some of these
are true lice, and some are allied parasites called false-scorpions or
chelifers. These are acquired whilst frequenting dung and refuse heaps,
where they abound; thus, probably cheese-mites and the like are conveyed
by flies into our larders and warehouses.

It is not only the web-weaving spiders which prey upon the proverbially
"silly" flies; there are also roving spiders which do not contrive webs,
and some of these are nocturnal feeders; the latter can only be seen in
daylight by looking for them underneath stones and in other hiding
places.

Other fly destroyers are internal parasites, and these include thread
worms (_Nematoidea_), as well as _Protozoa_ of obscure kinds. These are
being scientifically studied by experts, and their life-history is as
curious as that of others of the same order, in that they pass from one
host to another, which fact for long helped to baffle investigation.
Some have now been proved capable and others are suspect of baneful
possibilities.

The house-fly fungus, _Empusa muscæ_, which is prevalent in autumn, has
ever attracted popular wonder and much scientific attention. It has been
much written about and plentifully illustrated, but the complete
life-cycle of this peculiar parasitic growth is not yet understood; much
that has been published as of fact is mere "copy" repeated in one book
after another, originally in fact rather a matter of conjecture, based
upon the idea that fungic propagation must be on exactly parallel lines
with known biologic processes of a botanic order.

The house-fly fungus seems to have a superficial resemblance to some of
the common "moulds," but mycologically examined there is good reason for
classifying it with a family (_Entomophthoreæ_), which may be capable of
an alternative form of fructificative development.

The originating germ somehow at some time must be supposed to have
effected a lodgment in the body of the fly or possibly that of the
maggot. Later on, one cannot say when, fungic spawn (a pulpous mycelium)
starts a course of development, invades every part of the body, quickly
kills the fly, and fixes it to the spot to which in its last moments it
has crawled, often a window-pane. Its corpse is now swollen with the
spawn developed into masses termed hyphal; but these should not be
called hyphal (thread) but quasi-sclerotia, bodies intermediate in a
process of normal development between the mycelium and the fruiting
stage; fungic fructification ensues with great rapidity; and the corpse
becomes suffused with an appearance of white mouldy excrescences,
filiform conidiophores, of which the club-like tips make a copious ærial
discharge of white spores; when these adhere to a glass or window-pane
they imprint thereon a remarkable halo. Attempts to artificially infect
other flies with these spores are common failures or have led to
contrary conclusions.

The period from the first symptoms of distress to the death of the fly,
and from that time to the spore discharge is wonderfully short. The
infectious germs may have been long dormant in the fly, and very likely
may have been acquired in the maggot stage. In the absence of exact
knowledge, we can only make conjectures from observations of some
kindred fungic parasites, which are not very uncommon amongst the
chrysalids of certain moths, beetles, and the pupæ of some annual wild
bees. In these cases it seems very unlikely that the infection was
incurred otherwise than in the caterpillar or larval feeding stage.
Dampness and insanitary conditions seem to favour the spreading of such
disease, especially amongst artificially reared larvæ when crowded
together and closely confined.

Other kinds of flies do not, so often as the house-fly, perish from
_Empusa muscæ_, but I have seen a common yellow cowdung-fly, as early as
June, thus affected.

In spite of all antagonists the brood of the house-fly flourishes and
multiplies, but this is because great opportunity and encouragement is
provided by the neglect of good sanitation by mankind.




                               CHAPTER IX

                        DISSEMINATORS OF DISEASE


The house-fly may seem at first much less to be dreaded than any one of
the painfully "biting" or (to be correct) skin-piercing and
blood-sucking flies; yet it should be regarded as a much greater enemy
to humanity and a more dangerous peril than any of those other flies, of
which some short mention and description has now been given. Its
life-history and its fecundity have been already alluded to; its rapid
growth and maturity counterbalance the fact that it is short lived.

From ancient times there has been a consensus of opinion that there was
in some way a connection of cause and effect between swarms of flies and
the spread of disease. In the plagues of Egypt, in the reign of Pharaoh
of the Exodus, it will be remembered how, after "the land was corrupted
by reason of the swarms of flies," Exodus viii. 24, there came "a very
grievous murrain" upon cattle, Exodus ix. 3, followed by a "plague of
boils and blains" upon man and beast.

In our present day insect life is being scientifically investigated with
the view of establishing the connection, and of discovering fully the
serious _rôle_ of disseminating disease, of which the house-fly has long
been suspect. The microscope reveals much, and the art of bacterial
culture now explains how it is true that the superabundant creature,
which has persistently followed civilised man into every quarter of the
globe, has ever had a share in conveying contagion beyond that of any
other household pest.

That the house-fly is bred in filth matters not much. After emerging
from the puparium its first voidance of fæcal matter may be contaminated
with live baneful germs, but it voids itself before its first flight.
Having six legs it stands upon two pairs, whilst with the other pairs,
at one time the front pair and at another time the hind pair, it works
frequently and vigorously at brushing and stroking down every part of
its body. Though it starts its new life quite a wholesome newborn
creature, and though it must be credited with being a most assiduous
remover of dirt from its own body, yet from the human point of view its
subsequent life is a persistently disgraceful career.

It is the evil course of the newly-hatched and self-cleaned fly not to
restrict its diet to the honey of flowers, as do some of its relations.
Its food includes excrement, sputum, and every kind of putrefying
organic matter likely to be swarming with micro-organisms of a character
deleterious to humanity. It is certain that, when only a few days old, a
fly will practically abound internally and externally (on the feet) with
dangerous germs, as amply proved by methods of laboratory culture. As it
feeds, it walks over the food; and the hairy joints of its feet, when
microscopically viewed, appear conspicuously liable to carry germs in
spite of frequent attempts at self-cleaning. Wherever it alights and
walks, it prospects with a touch of its trunk, which is the main
instrument of evil. It has a very filthy habit, from time to time, of
depositing pale vomit spots as well as dark-coloured fæcal droppings.
These defilements are visible, wherever it may alight on walls, windows,
ceilings, and especially on pendent ornaments, whereon the males delight
to rest.

Its manner of feeding upon solid food is to pour forth a copious supply
of saliva, to regurgitate some previously imbibed fluid draught, and
then to re-imbibe; thus, besides devouring soft food, it dissolves,
befouls, and feeds on crystalline sugar and other hard dry food
materials.

Its regurgitated fluid commonly swarms with bacteria, microbes, and the
like. Imbibed bacteria are not inevitably killed in the digestive
process of the fly, for its excrement has been found to abound with well
recognisable infective germs. In the market, the shop, the larder, and
on our tables, the house-fly seeks every opportunity of befouling and
contaminating human food.

The varieties of micro-organisms are multitudinous, doubtless many more
in number than the microscopist and the bacteriologist expert have yet
isolated and registered as capable of identification. Granted that the
majority of these are non-pathogenic to humanity, still a formidable
number, including some which are very generally disseminated, are
virulently pathogenic, and many are suspect. There is no need to give a
list of all the infectious diseases which man and beast are liable to
contract, but the germs of nearly all may be carried from place to
place, from creature to creature, and from person to person, through the
intervention or agency of the house-fly. The medical profession are
convinced that infantile mortality from epidemic diarrhœa must be
attributable to summer flies.

In the matter of food which becomes fly-infected after having been
cooked, or of food like milk, butter, and fruit, which are consumed raw,
it should be known that a single pathogenic germ of ultra-microscopic
dimensions, having obtained lodgment in the body, may there multiply and
originate a fatal disease. On the other hand, raw meat which has been
infected may, after the bacteria have been all killed by cooking,
contain excreted poison in deleterious quantity. The decomposition of
infected meat begins ten or twelve hours before the bad odour is
perceptible.

Fortunately the omnipresent germs which most commonly deteriorate our
food are not very actively deleterious, or are only slightly
debilitating; yet wherever such less obnoxious germs get lodgment, there
the ready prepared and most favourable breeding place for the worser
kind is to be found. The various species of these evil things are not
always exterminating competitors; they sometimes flourish in company,
and dwell together, like the seven devils within the exorcised and sane
man after his relapse, as mentioned in the Scripture.

That food gets fly-blown and maggot-infected is a very disgusting fact,
but the plainly visible result is of little hygienic significance apart
from the more concealed facts of the fly-borne conveyance of zymotic
diseases.

Internal protozoal parasites and parasitic worms breed in and are
disseminated by the house-fly; so also are the fungic spores of
fermentive yeasts, of moulds, and the like, but these latter are mainly
disseminated by mere air currents. The eggs of tape-worms and the like
are carried by dung-frequenting flies to food, especially to semi-putrid
food devoured by dogs and pigs.

Some of the skin-piercing and blood-sucking flies are pestiferous in a
more direct way than any of the tribes of filth and sweat-flies. They
are the usual or suspected agents whereby anthrax, cattle-plague, swine
fever, glanders, and other diseases are spread far and wide. Some of
these last blood-sucking flies will travel with _and on_ the bodies of
transported animals for long distances; of course there can be no doubt
also as to the capability of disease dissemination by the direct
independent flight of flies to long distances with favouring weather and
breeze. Such evils are prevalent throughout the temperate zones, but
circumstances are far worse in the tropics, where _Glossina morsitans_,
considered by some to be a near relation of our _Stomoxys calcitrans_,
transmits the microscopic trypansomes which cause the devastating
"sleeping sickness" of mid-Africa. This last reference, and other
discoveries of the fly-borne germs of recurrent fevers, should bring
into prominent notice a very pertinent fact; which has not yet received
adequate scientific investigation. All the bites of our common
blood-sucking insects, flies, gnats, midges, fleas, etc., are each kind
of them wounds, sometimes very inflammatory, sometimes but little or not
at all so; furthermore, the worst inflammatory wounds not uncommonly
show feverish symptoms of a well marked periodic character, quiescent
intervals being followed by revived inflammation in the same spot. These
facts almost prove, or at least strongly suggest, an explanation that in
the latter cases the source of pathogenic trouble is of a microbic
character, and that periodic recurrence of feverish and inflammatory
symptoms is the time of the spore-swarming of breeding microbes; the
difference between these latter and those of a more severe and often
fatal kind in the tropics being that the one class finds the human body
a fit host in which to multiply but the other class does not, and
accordingly the latter grow weaker until their breed dies out. Similar
effects can be observed in cattle and other animals, but all creatures,
after suffering much from fly-bites at first, afterwards become for a
time more or less immune.




                               CHAPTER X

                           REMEDIAL MEASURES


We have seen in Chapter VIII that the checks which Nature has imposed
upon the prolific breeding of the house-fly have been insufficient to
protect civilised mankind from ancient times continuously up to the
present day. This defect need now no longer be endured; but, alas,
communities and individuals are ever slow to be warned, and averse to
practise newly advised methods of sanitation. In few other directions is
there greater promise of advancement in general public health and
comfort than by preventive measures against the breeding of the
house-fly. Effective measures comprehensible to all who consider the
subject are so easy of application, that, if universally carried out,
the house-fly might become a rare insect in a very few years' time. It
is, however, of fundamental importance that the public should be made to
comprehend the case; else the power necessary for enforcing suitable
regulations by the local authorities will not be obtainable.

Preventive measures must constitute the supreme objective of an anti-fly
crusade. The habits of the house-fly and its life-history make it clear
how successful breeding may be prevented. The breeding places are local
and accessible; the food substances of the larvæ are capable of being
put under control; and the maggot stage is the opportune period wherein
the fly plague is most obviously open to attack.

In all town and suburban parishes a house to house collection of
domestic refuse and garbage must be made, not weekly, but bi-weekly in
summer, and the material must be cremated in a dust destructor furnace
within a few days of its collection; thus neither larvæ nor pupæ therein
would survive; no alternative disposal otherwise than by cremation
should be attempted. Furthermore, and above all else, only refuse
collecting bins of an authorised pattern should be employed. Contrary to
the prevalent idea these should not be fly-proof and not have air-tight
covers; they should freely admit air all round and should encourage the
access of breeding flies. They should stand preferably in open daylight
places and should be egg-traps for flies which, thus encouraged, would
hardly ever deposit their eggs elsewhere; the result would be that all
maggots and pupæ would be inevitably cremated.

It may be objected that, if open dust-bins are used, house-flies after
visiting the same may return to the house and subsequently contaminate
food in the larder. There will be such a possibility, but the danger
thereof can be minimised, and would in fact be nearly automatically
cured, as prospective fly progeny perished. Furthermore, there are
circumstances which indicate that the said danger would not be great,
and anyhow nothing comparable to the baneful effects which are now
endured. The worst germs are not those of newly discarded food remnants;
the commonest and well-known bad smelling germ of ordinarily "tainted"
meat, which is exceptionally attractive to the house-fly and the
blue-bottle, is fortunately, after cooking, not so dangerous as some of
those other deleterious micro-organisms mentioned in the last chapter.
Taking one thing with another the balance of benefits and disadvantages
will incline overwhelmingly in favour of open dust-bins, wherein food
remnants may purposely become fly-blown. An improved dust-bin lid has
been contrived which combines with the cover a centrally held wire-gauze
"balloon" fly-trap, wherein flies will congregate and be imprisoned when
attempting to leave.

Unfortunately air-tight dust-bins have been very generally recommended
as a grand device of hygienic value; hence it is most necessary that
unthinking people at large should be informed how much better it is to
use open bins which can catch and secure for destruction prospective
fly-broods. It may be asked—why not trap and kill the breeding females?
The reply is that to do so will be good, as is to be explained in the
next chapter; but contrivances for the latter procedure are apt to be
less effectively put into general operation.

The fly swarms of mews, arising from accumulations of stable manure,
will be difficult to alleviate without stringently enforced measures,
but it is a mistaken notion to believe that town flies are bred in
stables to such an extent that the invaders of our dwellings and town
restaurants, shops, and markets, are merely or mainly the overflow of
the mews. The concentration of many kinds of flies is very dense around
ill-kept mews, and in midsummer-time a large percentage will be true
house-flies. Frequent removal and cremation of stable manure would be
quite effectual, but there is reason to think that, if proper care be
taken, no such drastic procedure as cremation will be absolutely
necessary, unless perhaps for the months of July and August.

There are two matters involved in sanitary stable reform—one is the
proper structure of the stable floor and the treatment of the litter
whilst in use for bedding; the other is the disposal of the horse
droppings and the discarded litter called stable manure. If the floor be
good and the bedding be well kept and fairly dry, which is often not the
case, then the effective breeding of flies will be in the dung-pit and
the external manure heap. From a sanitary point of view these latter are
indeed almost everywhere ill-kept.

The general fate of maggots living on the floor of well-kept horse-boxes
is to end their lives drowned in the drains to which they descend, when
or before they pupate.

In these days of motor-cars and fewer horses the horticulturist
everywhere is eager to buy good stuff; now stable manure to be good must
be fresh and free from the garbage with which stable men wantonly
corrupt the same, instead of consigning such extraneous refuse to a
proper separate dust-bin for collection and cremation. So much can be
done remuneratively with a regular supply of clean fresh manure, that it
seems almost worth while transgressing the proper limits of this booklet
and writing chapters on mushroom culture and on the intensive hot-bed
cultivation, with the aid of "cloches" or bell glasses, called French
gardening. It may be thought that such cultures will of themselves breed
swarms of flies. Though such is not necessarily the case, the liability
by common carelessness is very great.

The expert horticulturist has a special preparatory treatment for fresh
manure intended for hot-beds; new manure in heaps rapidly "heats," and
is ærated by being turned over two or three times on separate days
before being packed close for the hot-bed. This process of treatment
rather disagrees with the breeding of the house-fly. Mushrooms and all
the fungus tribe breathe by inhaling oxygen and exhaling carbon dioxide;
and so it happens that even insects which delight to feed on mushrooms,
are somewhat repelled by the special atmosphere of very actively growing
mycelium or spawn.

The amateur entomologist and the nature-student will observe that the
flies which pester the gardener at work are mainly other than the common
house-fly. The reader, nevertheless, will like to know if something more
cannot be done to stable manure for exterminating maggots, whether of
house-flies or the many various filth flies, already hatched and growing
therein. Well, "something" indeed can be done by the use of some
insecticide. Hitherto chloride of lime has been employed, but the most
approved insecticide for the purpose is a solution of iron sulphate—two
pounds in one gallon of water; this is said not to deteriorate the
horticultural value of stable manure. However, in fine weather, the
spreading out and drying of freshly received manure practically rids it
of fly maggots, which cannot survive this simple procedure. The mere
burial of fly-blown dung and stable litter without prior treatment is
quite inefficient. Insanitary heaps of neglected manure, which terribly
swarm with maggots, much deteriorate in horticultural value.

Farmyards and the scattered dwellings of rural districts remain to be
considered, and no doubt herein the difficulty is great, but not
hopeless. The latter will be persuaded to follow suit when the good
effects of town and suburban policy become apparent.

Something more than usual is desirable for the protection of cattle from
the breeze and the œstrid flies at midsummer. The latter, at all events,
could be easily exterminated by giving butterfly nets and encouragement
to children, who would enjoy the fun. Although the close approach of
strangers may alarm grazing animals, after the latter have galloped away
a very good chance will occur of capturing the slow flying gravid female
worble-fly with a butterfly net, or of felling her to the ground with a
suitable instrument; if missed on the first attempt, other chances can
be got again and again by waiting until the said same fly has returned
to threaten her intended victims. The writer has often succeeded in
felling the slow flying gravid female worble-fly with a mere walking
stick. It is strange that no farmers' entomological friend has hitherto
suggested so common-sense a remedy as butterfly nets, which should be of
a dark green colour. A company of our popular boy scouts, marching in a
skirmishing line on an August Bank Holiday (or a preceding Saturday),
over ground where grazing animals are observed showing behaviour
conspicuously indicative of attacks by œstrid flies, would enjoy doing
grandly useful execution. Every capture should be substantially
rewarded.

In an organised campaign of house-fly extermination it may rather be
expected that the principal trouble will be with the stable men of
unsanitary mews. In the United States of America very stringent bye-laws
have been made and enforced. Some of these, perhaps, deserve
consideration for adoption, with judicious improvements, in England, but
the policy of the OPEN DUST-BIN _and_ CREMATION raises new hopes of
success far beyond any advantages hitherto obtained in America.




                               CHAPTER XI

                        CONTROL WITHIN THE HOUSE


Many minor plans have been proposed for obviating or alleviating the
perils and plague of invading fly swarms; several such plans may be well
carried out on a private domestic scale, but one cannot expect any of
them to be adopted universally. In domestic methods people will prefer
some one plan, some another, whilst some will not personally aid in the
work of fly destruction in any single way perseveringly. This latter
circumstance emphasises the necessity of a dominant control by local
authority for the safeguarding of all inhabitants, including the
delinquents themselves in spite of themselves.

The plan, as detailed in the last chapter, of enticing breeding females
to lay their eggs within depositories of discarded food remnants and
garbage, can be practised on a smaller scale with great advantage
everywhere. Kitchen refuse of many kinds, not neglecting potato and
turnip parings, cabbage leaves, or even tea leaves, should all be
collected in brown paper bags, which should be left open for a few days
in suitable places round about the house for the free access of gravid
female house-flies. Every such collection should he cremated on the
third day. In a paper, read at a recent congress of the Royal Sanitary
Institute, on "Destruction and Prevention of Household Pests," Dr. Gay
advised rich and poor, in every household, whether or not a sanitary
dust-bin was in use, instantly to _wrap up in paper_ all such
fly-breeding materials in readiness for cremation. However, to do so
would be missing the much more effectual course of applying my
"egg-trap" plan of collections in exposed _open bags_ for cremation on
the third day.

For indoor use insecticide methods are more suited; and the best of
these are immensely more effective than some popular devices, which make
a remarkable display and sell well, but which the purchasers soon become
neglectful to keep in constant use. Traps in the form of wire-gauze
cages, and glass non-return bottles belong to this latter class of
contrivances; when seen crowded with struggling victims, the employment
of such articles captivates many observers; but their real efficiency
will be found to fall far short of general expectation. The explanation
will be apparent when the use of the wire-cage trap is contrasted with
the success of a good fly poison. Given, say, a dwelling room on a
midsummer day containing ten female flies and ten idle dancing male
flies; in such cases not more than half the females and one quarter of
the males will get imprisoned within four or five hours by the
employment of the wire-cage trap, but with a good method of setting
poison nine-tenths of the females and half the males may be killed
within the same period. In the case of poisoning, the dead have to be
swept up, whilst fly traps have the advantage of collecting the victims;
but, unless the inmates are carefully destroyed, a few will manage
sometimes to escape from the traps, especially as side window light
changes and daylight fades. In these fly traps it is only the
perseverance of the prisoners in struggling towards outer light which
prevents their exit by the entrance aperture.

Stickfast adhesive papers and suspended tapes and strings look very
effective when seen crowded with accumulated captures; but, again, these
"exhibition" appearances are as deceptive in suggestions of real
efficiency as are the crowded cage traps last mentioned; moreover,
sticky messes are not commendable or convenient articles for placing
where most wanted. Truly, suspensory strings are attractive resting
resorts for dancing males, but the worst agents of Beelzebub are the
females, which have a keener appetite for food and for pestering
humanity.

There remain for consideration insecticide poisons. A great choice of
materials can be supplied by the chemist's shop, and various methods of
using them have been recommended. In old times country people prepared
decoctions of _Amanita muscaria_, the fly toadstool, a large
orange-scarlet, or crimson, mushroom-shaped fungus commonly appearing in
autumn in woods where birch trees abound. Strange to say, such decoction
will poison flies of many kinds, although they, and many different
creatures, feed with impunity on other fungi which are more deadly
poisonous to mankind.

Effective poisons are such good exterminators of flies, that the main
consideration is how to safely and most suitably employ them. There are
some people who have an invincible aversion to the mere thought of
poison purposely administered by way of food or drink, though possibly
they do not have an equally strong repugnance to the use of insecticides
used for stifling. However, one cannot help running counter to much
misplaced sentimental humanitarianism in some people on some subjects;
reasons and arguments will not move them, for they do not wish to think
otherwise than as their prejudices influence them. The house-fly is
itself a poisoner of our food, and it, or rather she (the offender being
nearly always female), is a more dangerous and a more subtilely baneful
enemy than, for instance, the human flea, which even the Brahmans or the
disciples of Buddha may kill.

Fumigatory insecticides, though occasionally useful, may be left out of
consideration in discussing the rival merits of means in a warfare
against the house-fly.

A liquid or moist food poison employed in a safe and effective way will
excel every other weapon of warfare within the house. One of the newest
recommended substances is formalin, which has the advantages of being a
disinfectant, a strong fly-poison not avoided by flies, and not
dangerous or attractive to domestic animals. A tablespoonful of (40 per
cent.) formalin should be mixed with one half pint of milk and water;
this, when exposed in saucers or shallow dishes, is said to be an
attractive and a fatal bait. It would be evidently dangerous and
objectionable to use some other commoner poisons in the same way; but it
is the opinion of some users that formalin and milk is not sufficiently
alluring.

Contrary to a generally prevalent idea a powerful odour is not required
as an indoor allurement for the common house-fly; again, a saucer or
shallow dish with liquid contents is not a good _method_ of presenting
the fatal bait. Placed on a table, or on a window sill, or on a shelf, a
saucer is liable to be tipped up and its contents spilt; moreover, the
form of such receptacles is radically faulty by reason of the strenuous
walking habits of the fly on the level. Out of many flies walking over a
table ten or twelve may pass by, or round, an overhanging saucer's rim
to one fly that will mount the same and sip inside. However, let such a
saucer or plate be placed on a table upside-down, and let a slightly
moist substance be placed in the shallow central depression, which
ordinarily is the base, then the said ten or twelve flies will all mount
and sample the moist substance, even though it be not apparently
attractive in smell; an inclined plane is ever an irresistible
invitation to mount and prospect the summit.

It is another great mistake to suppose that an extra tasty food material
is desirable as a bait. The same kind of mistake is made by people
baiting a mouse trap with toasted cheese, whilst a bit of dry bread, or
better still, a green pea, would much better entice a common mouse.
Strong smelling and saccharine foods immensely attract the blue-bottle
and the wasp, which are thus enticed indoors and induced to become
occasional visitors to our tables; but the house-fly requires little of
such lures; indoors she is an inquisitive prospector, who will never
pass by any moist material without testing its quality. Moreover, the
use of poisoned milk, or even jam, should be rather avoided for fear of
injury to dog or cat; furthermore, it is dangerous to place a piece of
bread in a saucer of liquid fly-poison, as is sometimes done, to serve
as a sop and as a standing stage. However, there is one good lure well
worth mentioning; it is beer-dregs with or without a little sugar;
moistened yeast is good, and the advantage of beer-dregs with just a
little sugar is due to the mild yeast-like odour of slow fermentation,
which may fail if formalin be the insecticide ingredient.

The handiest and safest preparation of fly-poison is that sold in the
form of a dry flypaper, which is said to contain arsenic as the deadly
ingredient. A very small piece of one of the sheets ordinarily sold
should be placed on the summit of an inverted saucer; a mere spoonful of
water now and then will suffice to moisten the same; there is little or
no advantage in sprinkling a little sugar thereon, unless beer-dregs are
added. This plan of using moistened poison paper is clean; it is safer
than using a more fluid bait, and the ingredient is certainly efficient;
the slightest taste thereof by an inquisitive fly ensures its speedy
death. Another poison which has been recommended is a strong decoction
of tea-leaves, to which a little sugar and beer may perhaps be added.

It is said that the smell of geraniums is odious to the house-fly, and
so pots of these plants may be grown beneficially on window-sills.
Certain other odours and scents are believed to be likewise more or less
fly deterrent, but their use is not effective warfare against fly
propagation. Paraffin painted on window-sills is said to be very
efficient.

Flies may be easily prevented from entering the open windows of any
room, which has windows only on one side, by the use of venetian or
louvre blinds or shutters, or of many kinds of screens, although the
apertures thereof may allow of ample room for flies to pass to and fro.
If, however, there be windows on two sides of a room, then venetian
blinds and the like will be useless, and window screens must have very
close meshes to be effective. The house-fly will pass through netting
only when there is light shining on the further side. A knowledge of
this fact is very important in the planning of hospital wards. In a sick
room, if there be windows on two sides, one in summer time should be
darkened when the other is open for ventilation.

The protection of the larder and the screening of food should never be
neglected, but what is of even greater importance is the prevention of
access by flies to fæcal matter, or to purulent and all unhealthy
discharges from the sick room.




                              CHAPTER XII

                    THE SERVICE AND UTILITY OF FLIES


It is often asked—have not house-flies some use in Nature? The only true
answer is that they are warning signals.

They certainly do join with a multitude of other flies in promiscuous
scavenging services, and they can be very active agents therein; but
this work only aggravates the fact of their dangerous partiality to
mankind, together with all his belongings and surroundings. These
creatures may well be imagined to have developed out of some primæval
species by reason of the increase of mankind upon this planet. The mere
presence of the house-fly denotes some nuisance more or less remote; the
local density of the brood indicates the degree and the proximity of
unsanitary conditions. Under present circumstances the visitation of the
house-fly is Nature's intimation that peril of a very insidious
character is about. Very properly, Nature's messenger will not be
denied, and pertinaciously manifests herself to us _indoors_!

It has already been explained that the scavenging service of the
house-fly can be altogether dispensed with, inasmuch as there is a
sufficiency of other less noxious flies and creatures devoted to such
work. Reflecting on the Story of Creation, and the mission of man as
first a gardener, and then, when expelled from Paradise, destined to
more laboriously cultivate the earth, it may be held to be man's
allotted duty not only to wage war against weeds, but likewise to
distinguish friends and foes of all kinds, and treat accordingly
creatures even of all branches of the animal kingdom, whether insects,
reptiles, birds, or mammals, favouring one and exterminating another.
This will be to rule the earth and "subdue it" (Genesis i. 28). Nemesis
will inevitably chastise man unless he rectifies the consequences of his
own delinquencies, whether they be direct or indirect. The "good
service" of the house-fly is comparable with that of the flea, which
performs an unwelcomed and indirect "service," inciting the housewife to
have well-swept floors and clean bedding.

The unalloyed good service of insectivorous flies is quite apparent. The
details of their life-history and a description of their different
characteristics would make an interesting volume, but the limitations of
the present work preclude such enlargement of its scope.

It certainly stands to the credit of the blue-bottle that she is by far
our best native scavenger of carrion; so good, indeed, that none other
as an assistant is needed. She may just possibly sometimes convey germs
and contaminate food, but she does not so directly assail man. Her
larger size makes her easy for exclusion from the domestic food store.
So eager and alert is the female in searching for meat, dead animals,
and fish, that our other native carrion-feeding flies are at a great
disadvantage in the struggle for existence; so prompt is she in
monopolising carrion, that would-be competitors often have to be content
with laying their eggs in less rich food materials. The blue-bottle can
withstand temperatures a few degrees colder than can those flies to
which she is nearest akin; and she seems capable somehow of sheltering
herself better. Even as late as the middle of winter, sometimes, a dead
bird may be found to be fly-blown under circumstances which indicate
that the eggs must have been laid in frosty weather, when flies are not
seen at large. The explanation is that the blue-bottle will for a short
time awake, and venture outside her retreat in a sheltered south wall,
warmed by a few hours of winter sun. She does not hibernate in early
winter in such a continuous state of rigid torpor as, for instance, does
the queen wasp; probably few or none survive the winter by a real
hibernation, the progenitors of the first spring broods emerging at a
date no earlier than do their rivals and congeners.

As a bird food or a fishing bait gentles are superior to the maggots of
any other dipterid insect. So-called ants' eggs and meal-worms are more
highly appreciated by the fancier for bird food, but they are expensive.
The pupæ called "ants' eggs" can only be had fresh for a short period of
summer, and dried stock for the rest of the year requires much labour to
obtain and prepare. Meal-worms are the cleanest and the easiest to
propagate of all similar larvæ; but they are very slow growing compared
with gentles; in the natural state the life-cycle from the egg to the
feeding worm, then the pupa or chrysalid, and finally the beetle,
_Tenebrio molitor_, occupies a twelvemonth's time; but, like many other
insects which have accommodated themselves to human surroundings, they
can increase more rapidly. By rearing a number of broods, each in a
separate vessel, and by hastening the development and propagation of
some broods more than others, meal-worms may be obtained fresh
throughout the year; the amount of trouble and attention required is
accordingly great.

The artificial rearing of gentles is easy, rapid, and cheap. Generally
it is not well or methodically managed, and consequently it is then a
horribly malodorous nuisance. However, with proper care the process can
be managed without offensiveness, and it will immensely repay all
trouble.

A more restricted variety of birds relish gentles, but no insect food is
more wholesome for any of the galinaceous tribe.

A spot in the open air, preferably sheltered from the north or east wind
and from mid-day sun, should be chosen. There an inverted earthenware
sea-kale pot or a similar vessel should be fixed on a stand or table
twenty inches high from the ground; the table should have a central hole
corresponding to that in the sea-kale pot. The hole in the pot should be
obstructed with a wire-cage strainer, or a piece of perforated wood or
metal, above which a few sticks or a bunch of straw may be placed.

[Illustration:

  Fig. 6.

  Apparatus for the
  cleaner breeding
  of gentles.
]

Fly-blown dead animals, fish, offal, or suitable food remnants should be
placed from time to time in such a receptacle, which should be
surmounted with a removable rain-proof cover and shade of ample size.
The latter should allow a two-inch space or a little more underneath all
around the rim of the pot for ventilation. Underneath the table or stand
a wide and more or less shallow pan or dish should be placed, and a
little clean sharp sand placed therein.

The gentles, whilst growing and feeding, are called "green" gentles;
their skin is transparent, and in this state chickens do not like eating
them; and it is as well so, for then the half-grown gentles would be
capable of temporarily becoming deleterious internal parasites in the
birds' crop. As soon as they are full grown they crawl away from the
food material and will fall through the strainer-like obstruction in the
bottom hole of the pot into the pan on the ground underneath. They are
then termed clean or "scoured" gentles and are fit for bird-food or for
fishing-bait.

If taken out of the pan and placed in boxes with a little sand, they
will keep three days, more or less, according to the weather; they then
pupate, and in a few days, or weeks, or months, according to
temperature, emerge as blue-bottles. As pupæ they are good and
convenient food for domestic fowls, and for all pheasants and like
game-birds.

If receptacles as above directed are situate in a fowl-run, the hens
will never leave the ground dish unwatched as long as full fed gentles
are maturing. Hens thus fed are prolific layers of eggs, but of course
they must be otherwise fairly fed with farinaceous and suitable other
food and healthy grit. The maggots of no other flies are worth similarly
cultivating; those that feed on vegetable refuse are more offensive in
smell than common gentles; the maggots of the fungus flies are
comparatively clean creatures and free from bad smell, but the largest
are small.




                              CHAPTER XIII

                    A CAMPAIGN OF EFFECTIVE WARFARE


Several authors of recent books, and lately also able lecturers, have
done much to awaken people to a realisation of the dangers of our ever
recurrent summer plague of flies. The advent of the petrol motor-car and
other automobile vehicles has at the most but very slightly improved the
state of affairs within town areas, where mews were formerly much more
numerous. The public press has followed suit, but something more in the
way of a sustained effort for hygienic reform is desirable. The terrible
European war should not preclude consideration of the subject, for the
scourges of fly-borne contagion have ever followed armies and rivalled
the casualties of the very battlefield. Bands of enthusiasts everywhere
should keep going a veritable anti-fly campaign as one of the most
urgent needs of practical sanitation. Otherwise active support of the
cause will soon languish and be obliterated amongst the multitudinous
ever-changing questions of the day, political and other, which, as
newspaper editors are persuaded, have the attention of the public for
the time being. In spite of the incontestible prospects of universal
benefit it may not be easy to engage a large body of public support
without something like an organised propagandist movement.

If any readers of this booklet are disposed to join and form a central
body with a view of ultimately founding an association for promoting the
work of fly extermination, the writer will be glad to find or meet with
an honorary secretary and helpers who will work in the cause and
economise in the necessary expenditure of all contributions received.
After the preliminary efforts of starting such an association, its work
will be not only to urge the local sanitary authorities everywhere to
adopt the best possible course of action, but also to incessantly move
public opinion to compel Parliament to pass laws, capable of
administration, for the public welfare in this matter.

The present booklet had its origin very many years ago in the author's
idea of writing an account of the house-fly and its kindred, which would
be interesting and more truthful than much then to be found in current
literature. Such off-hand inconsiderate writing, as appears in the
"Elements of Entomology," by W. S. Dallas, F.L.S., requires to be
controverted; therein it is stated that the house-fly, which is
"troublesome, does very little actual damage, for our only real grounds
of complaint are to be summed up in the tickling sensation which its
feet cause," &c. "In its larvæ state, however, it lives inoffensively
enough in dung." It has now seemed timely to publish my long-delayed
work, re-written with the object of more urgently interesting the
general public in the cause of the anti-fly campaign. Still, the author
trusts that both the deeper and the less entomologically inclined nature
students will find therein not only useful, but also some novel
information, given with not too much entomological technicality.

There is no English work sufficiently modern and comprehensive for a
study of our native flies. In 1776, Moses Harris, who originated or
elaborated the study of wing patterns, published his "Exposition of
English Insects," in which more than 300 flies are figured and
described; they have the old Linnæan classification and nomenclature, of
course, and the work is scarce. All later attempts by English authors in
the way of a more comprehensive student's guide book have been left
incomplete. Another excellent, but expensive work, Curtis's "Genera of
British Insects," contains about 250 illustrations and descriptions of
flies; but most of these are rather rarities, and the amateur in search
of a facile guide to the commoner objects of the country-side will be
apt to be disappointed. For the sake of readers possibly eager of
advancing further in the study, and in the absence of any commendable
guide book, a short appendix has been added to the present work, for
help in identifying more numerous species and those of many families and
genera not mentioned in the foregoing pages. With the leave of the
Northumberland, Durham, and Newcastle-upon-Tyne Natural History Society
some valuable plates of illustrations are herewith reprinted, and
explanatory notes are added, mainly from the volume of the Society's
transactions for 1906, a most valuable work and compilation by the late
Rev. W. J. Wingate, of Bishop Auckland. This learned entomologist has
succeeded in giving a marvellously comprehensive amount of clear
condensed guidance. It is a great privilege that the present booklet has
been allowed to borrow from such a source of knowledge, valuable far
beyond the locality of its authorship.

Other illustrations which have been borrowed appear with the leave of
His Majesty's Office of Works, out of Reports to the Local Government on
Public Health and Medical Subjects.

[Illustration:

  FLY CHART.

  PLATE I. (APPENDIX)
]




                                APPENDIX




                       INDEX TO TERMS AND SYMBOLS
                                 OF THE
                     WINGATE FLY CHART, _PLATE_ I.


This Index, together with the following "Table of Wing-cells and Veins,"
the "Glossary," and _plates_, II, III, IV, V, VI and VII, will explain
the theoretical Diagram entitled The Fly Chart, illustrating
characteristic features and exterior parts, by the study of which the
reader may learn to differentiate all the sixty families which contain
species native to Great Britain.

A = the Head, comprising nine regions and parts (A, I to A, IX).

A, I, the Vertex, which contains (1) the Ocellar Triangle; (2) the
Ocelli; (3) the Vertical Triangle, a coloured patch surrounding the
ocellar triangle; (7) the Vertical Orbit, the sides of the vertex close
to the compound eyes. The Bristles hereabouts are (4) the Vertical
(inner and outer); (5) the Post-vertical; and (6) the Ocellar.

A, II, the Compound Eyes, large and often hairy.

A, III, the Frons is the forehead between the eyes; it contains (1) the
Frontal Stripe; (2) the Frontal Orbits at the sides of the frontal
stripe; (3) the Frontal Lunule (_plate_ VII, 5) a crescent immediately
above the antennæ. The Bristles hereabouts are (4) one pair of Frontal;
a row, or rows of (5) Fronto-orbital; and (6) Lower Fronto-orbital. The
(7) Eye Margin is a narrow, often glistening, white line close to the
eye.

A, IV, Antennæ, jointed processes springing from between the eyes just
below the frons; those with numerous joints are illustrated in _plate_
II, others in _plate_ III. The Frontal Suture in the middle of the face
is a little pit in which short antennæ often lie close together. The (1)
Basal Joints are the two next the head; (2) the Flagellum, all the
joints, when numerous, taken together; (3) the First Joint is next the
head; (4) the Second Joint; (5) the third Joint (_plate_ III, 1-9) is
sometimes ringed; (6) the Arista, or Seta, is a plume, spine, or bristle
springing from the third joint at some point of its upper surface
between the base and the tip.

A, V, the Face is the region above the so-called mouth and below the
antennæ; the ridges bounding the face on each side are (1) the Facialia;
here are (2) the Facial Bristles; (3) the Mystax (_pl._ VI, _fig._ 28)
is peculiar.

A, VI, the Cheeks, spaces at the sides between A, II and A, V (I).

A, VII, the Jowls, parts below A, VI and the so-called mouth.

A, VIII, the Mouth, more or less of a cavity into which (3) the
Proboscis (the jointed sucking trunk) can be sometimes partly withdrawn;
the proboscis has a basal joint called the Rostrum (a snout); the other
joint is called the Haustellum (a pump) and has the tip variously
adapted as for mere surface suction, or for deep insertion, or for
piercing. (1) the Peristome is the region surrounding the mouth; (2) the
Vibrissæ are strong bristles close to the sides of the mouth, or A, V
(I); (4) the Palpi, two feelers (or perhaps smelling organs) attached to
the proboscis.

A, IX, the Back of the Head; here (I) Post-orbital Bristles are
sometimes found, that is to say, behind the eyes, A, II.

B = the Thorax, the middle portion of the fly bearing the organs of
locomotion.

B, I, the Dorsum. The diagram on _plate_ VI, _fig._ 40 illustrates the
upper surface of this region; this part is bounded in front by (_a_) the
Neck; behind by (_b_) the Scutellar Suture (15) or Seam; at the sides by
(_c_) the Dorso-pleural Sutures (9-9) running from the front corners to
the front of the Wing Bases; by (_d_) the Wing Bases (10-10); and by
(_e_) the Scutellar Bridges, which are ridges (11-11) running with right
and left inclines to the root of (6) the Scutellum. The Dorsum is
crossed by (8) the Dorsal Suture, behind which are the Alar Regions
(5-5); here on each side is a ridge (12-12) the Alar Frenum; rows of
minute bristles on the centre are termed Acrostichal.

B, II, the Sides, or Pleuræ, specified separately in connection with—

B, III, the Breast, or Sternum; (1) the Prothorax is below the shoulder
and above the fore-leg; (2) the Meso-pleura is contiguous to the
prothorax and the shoulder; here in the upper front corner is the
"Stigma," a prominent respiratory orifice, below which the large
Stigmatical Bristle may be found; the (3) Ptero-pleura is below the
wings and behind the meso-pleura; (4) the Meta-pleura is "a more or less
tubercular piece below the region between the root of the wing and the
haltere"; (5) the Sterno-pleura is above the middle leg and below the
Sterno-pleural Suture, where it bounds the meso-pleura; (6) the
Hypo-pleura is behind the sterno-pleura and above the hind leg.

B, IV, the Meta-Notum is the part of the thorax behind and beneath B, I
(6), the scutellum.

C = Appendages of the thorax.

C, I, Fore-legs, Mid-legs, and Hind-legs; every leg has nine joints
[particularised illustrations on _plate_ VII]; (1) Coxæ are the joints
attached to the body; (2) Trochanters very small and inconspicuous; (3)
Femora or Thighs; (4) Tibiæ or Shins; (5) First Tarsal Joint or
Metatarsus; (6) Second Tarsal Joint; (7) Third; (8) Fourth; (9) Fifth
Tarsal Joint; (10) the Knees are where the Thighs and Shins join; (11)
Claws, Foot-pads, and Empodium are appendages of the fifth tarsal joint.

C, II, Wings [_see_ Table of wing-cells and veins]; the quarters of the
wing are the Fore and the Hind Basal Regions and the Fore and the Hind
Apical Regions. The Stigma is a thickened portion of the wing at the
middle of the fore margin.

C, III, the Halteres.

C, IV, Squamæ are scale-like appendages beneath the wings and above the
halteres; they seem to have some attachment to the roots of the wings; a
small inner lobe is called the antisquama, but it is a feature not of
much use in classifying and differentiating species.

D = the Abdomen has numerous ringed sections; in the Sub-order,
Cyclorrhapha in eight segments, but commonly divided into four or five
conspicuous segments and three or four more smaller, less visible, and
much modified in the sexual terminal segments.

D, I, the first abdominal segment is the Basal Segment.

D, II, the last of those more visible is the Anal Segment or Anus.

D, III, the abdominal termination, _see plate_ VI, _fig._ 17.

D, IV, the chief segments consist each of an Upper Plate joined to an
Under Plate by Membranous Sides, often concealed.

D, V, Abdominal Bristles, _see plate_ VI, _fig._ 41.

E = Bristles, Hairs, etc.; fine short furry hairs are called Pubescence;
"Hairs" are longer and stronger; Bristles are still stronger; but a very
thick bristle is called a Spine, if on the costa, and a Spur, if on the
leg; the larger bristles on B or on D are called Macrochætæ.

F = Stripes and Bands; a long marking, when parallel (or nearly so) to
the major axis of the body, leg, or wing, is called a Stripe; when lying
at right angles (or nearly so) it is called a Band. For "frontal stripe"
_see_ A, III (1).

O = Cells of the wing [_see_ the following Table]; the rib-like nervures
are termed Veins; these divide the area of the wing into more or less
twelve compartments called Cells or Areolets.

V = Longitudinal Veins [_see_ the following Table]; two groupings within
the margin can be recognised; the principal veins of the Fore Region are
numbered, 1, 2, and 3, whilst those of the Hind Region are numbered, 4,
5, 6 and 7 respectively; some have branches, _a_, _b_, _c_, etc., when
sections (separately referred to) may have index numerals attached.

X = Cross-Veins [_see_ the following Table]; one very significant X-vein
termed X, 4 (or the Discal X) in the middle of the wing connects the
longitudinal V, 4 to the V, 3, which are thus to be identified even in
very abnormal patterns.

The cross-veins and cells are symbolised by having attached to the
letters X and O respectively the indicative and qualifying figures and
letters belonging to the V upon which they rest, that is to say, the V
(or part of V) which is the lower boundary.




                     TABLE OF WING CELLS AND VEINS


O, 1.—Costal Cell (undivided), or Costal Areolet.

O, 1_a_^1.—The Humeral Cell }

O, 1_a_^2.—Second Costal Cell } Costal Cell, when divided.

O, 1_b_.—Subcostal Cell }

O, 2.—Marginal Cell (resting on V, 2).

O, 3.—Submarginal Cell (resting on V, 3).

O, 4^1.—Cell resting on 4^1 (the 1st part of V, 4), a "basal" cell.

O, 4^2.—Cell resting on 4^2 (the 2nd part of V, 4).

O, 4_b_.—Cell resting on 4_b_ (a lower branch of V, 4).

O, 5^1.—Cell resting on 5^1 (the 1st part of V, 5), a "basal" cell.

O, 5^2.—Cell resting on 5^2 (the 2nd part of V, 5), a "discal" cell.

O, 5^3.—Cell resting on 5^3 (the 3rd part of V, 5), a "marginal" cell.

O, 6.—The Anal Cell.

O, 7.—The Axillary Cell.

O, 8.—The Subaxillary Cell.

O, 9.—The Alula, or Axillary Lobe.

V, _c_ (or C).—The Costal Vein, or Costa, bounding the front Margin.

V, _c_1_a_.—Part of the Costa (often ciliated and spined) reaching to
the end of V, 1_a_.

V, 1_a_.—The upper branch of the V, 1.

V, 1_b_.—The lower branch of the V, 1.

V, 2.—Second (longitudinal) Vein.

V, 2_b_.—Lower branch of V, 2.

V, 3.—Third or Cubital Vein.

V, _s_.—The "Vena Spuria," a thickening of the wing (characteristic of
Syrphidæ), an imperfect V between V, 3 and V, 4 crossing X, 4.

V, _h_.—A "Hang" V (or Appendix) a more or less irregular incomplete V.

V, 4.—Fourth Vein, often much branching.

V, 5.—Fifth Vein.

V, 6.—The Anal Vein.

V, 7.—The Axillary Vein.

X, 1_a_.—The Humeral Cross-vein, connecting V, 1_a_ to V, _c_.

X, 1_b_.—The Subcostal X-vein, connecting V, 1_b_ to V, 1_a_.

X, 2.—Cross-vein connecting V, 2 to V, 1_b_.

X, 4.—Discal, Middle, or Central X-vein.

X, 5^1.—Lower Cross-vein, connecting V, 5^1 to V, 4.

X, 5^2.—Lower Marginal Cross-vein, connecting V, 5^2 to V, 4 (or to some
branch of V, 4).

X, 6.—Anal Cross-vein.




                      GLOSSARY OF TERMS WITH INDEX
                               REFERENCES


 Abdomen D

 Acrostichal B, I

 Alar frena B, I (12-12)

 Alula, or Axillary lobe O, 9

 Anal Vein V, 6

 Antennæ, or Horns A, IV

 Anus D, II

 Apical Region C, II

 Arista, or Seta [_plate_ III] A, IV (6)

 Axillary Vein V, 7


 Basal Region C, II

 Breast, or Sternum B, III

 Bristles, Spines, Hair, etc. E


 Calcar, Spur, or Thorn E

 Cells of Wings, or Areolets O

 Cheeks or Genæ A, VI

 Costa V, _c_

 Coxæ, or body-joints C, I (1)

 Cubital Vein V, 3


 Dorsum [_plate_ VI] B, I


 Empodium, claws and pads C, I (11)

 Eye Margin A, III (7)


 Face and Facialia A, V

 Femora, or Thighs C, I (3)

 Forceps [_plate_ VI, _fig._ 17]

 Frons A, III

 Frontal Lunule [_plate_ VII, 5] A, III (3)

 Frontal Stripe A, III (1)

 Frontal Suture A, IV


 Halteres C, III

 Hang Vein, or Appendix V, _h_

 Hypo-pleura B, III (6)


 Jowls A, VII


 Knees C, I (10)

 Meso-pleura B, III (2)

 Meta Notum B, IV

 Meta-pleura B, III (4)

 Meta-tarsus C, I (5)

 Mouth A, VIII

 Mystax A, V (3)


 O = Cell of wing C, II

 Ocelli A, I (2)

 Ocellar Triangle A, I (1)

 Orbits A, I (7) and A, III (2)


 Palpi A, VIII (4)

 Peristome A, VIII (1)

 Pleuræ, or Side regions B, II

 Proboscis A, VIII (3)

 Prothorax B, III (1)

 Ptero-pleura B, III (3)


 Scutellum B, I (6)

 Scutellar Bridges B, I (11-11)

 Shoulders or Humeri [_plate_ VI, 40] B, I (1-1)

 Squamæ, or Calyptræ C, IV

 Sterno-pleura B, III (5)

 Stigma of Pleura B, III (2)

 Stigma of Wing C, II

 Stripe or Band F

 Sutures A, IV, and B, I


 Tarsi, or Tarsal (foot) Joints C, I (5-9)

 Tibiæ, or Shins C, I (4)

 Thorax B

 Trochanter C, I (2)


 V = longitudinal Veins C, II

 Vena Spuria V, _s_

 Vertex, or Crown A, I

 Vibrissæ, or Mouth Bristles A, VIII (2)


 X = Cross-Veins of Wings C, II




                      ALPHABETIC LIST OF FAMILIES


             Name                Family            Analytic
                                    No.                Ref.

             Agromyzidæ            LIII            127, 138
             Anthomyidæ          XXXIII                  74
             Asilidæ              XVIII                  40
             Astiadæ                 LV                 126
             Bibionidæ               IV                  11
             Bombylidæ              XIX                  42
             Borboridæ              LVI                 106
             Braulidæ               LIX                 143
             Cecidomyidæ             II                   3
             Chironomidæ             VI                  14
             Chloropidæ              LI                 111
             Conopidæ              XXIX              54, 60
             Cordyluridæ          XXXIV                  82
             Culicidæ                IX                  18
             Cyrtidæ               XXII                  38
             Dixidæ                   X               19_a_
             Dolicopodidæ          XXIV              50, 65
             Drosophilidæ             L            114, 131
             Empidæ               XXIII       45, 49, 66_a_
             Ephydridæ             XLIX                 113
             Geomyzidæ           XLVIII                 132
             Helomyzidæ           XXXVI                  80
             Heteroneuridæ       XXXVII                  78
             Hippoboscidæ         LVIII                 144
             Leptidæ               XVII              31, 37
             Limnobidæ              XII                  23
             Lonchæidæ            XLIII                  92
             Lonchopteridæ          XXV                  51
             Micropezidæ             XL            103, 109
             Milichidæ              LII                 129
             Muscidæ              XXXII                  73
             Mycetophilidæ          III                  10
             Nycteribidæ             LX                 145
             Œstridæ                XXX                  62
             Opomyzidæ              XLV                 139
             Orphnephilidae         VII               19_b_
             Ortalidæ               XLI             87, 104
             Phoridæ               LVII                 140
             Phycodromidæ          XXXV             89, 116
             Phytomyzidæ            LIV             68, 125
             Piophilidæ           XLVII                 120
             Pipunculidæ          XXVII                  58
             Platypezidæ           XXVI                  53
             Psilidæ              XXXIX            101, 135
             Psychodidæ            VIII                  16
             Ptychopteridæ           XI                  21
             Pulicidæ                 I                   0
             Rhyphidæ               XIV                   8
             Sapromyzidæ           XLIV                  93
             Scenopinidæ            XXI                  44
             Sciomyzidæ         XXXVIII              86, 95
             Sepsidæ               XLVI   83, 102, 121, 136
             Simulidæ                 V                  13
             Stratiomyidæ            XV                  28
             Syrphidæ            XXVIII                  59
             Tabanidæ               XVI                  30
             Tachinidæ             XXXI                  72
             Therevidæ               XX                  43
             Tipulidæ              XIII                  24
             Trypetidæ             XLII                  97


                                PLATE II

      _Family Type-Forms of Antennæ in the first section, or Flies
                  with many-jointed Antennæ—NEMOCERA_


II.—CECIDOMYIDÆ

1. Epidosis longipes, ♂

2. Asphondylia sarothamni


III.—MYCETOPHILIDÆ

3. Sciara thomæ

4. Mycetophila cingulum

5. Mycetobia pallipes

6. Macrocera lutea


IV.—BIBIONIDÆ

7. Bibio marci, ♀

8. Scatopse notata


V.—SIMULIDÆ

9. Simulium reptans


VI.—CHIRONOMIDÆ

10. Chironomus plumosus

11. Ceratopogon femoratus, ⚲

12. Clunio marinus


IX.—CULICIDÆ

13. Mochlonyx velutinus

14. Corethra plumicornis, ♀


XII.—LIMNOBIDÆ

15. Limnophila dispar

16. Rhipidia maculata, ⚲

17. Erioptera flavescens

18. Trichocera hiemalis


XI.—PTYCHOPTERIDÆ

19. Ptychoptera contaminata


XIII.—TIPULIDÆ

20. Tipula gigantea

21. Ctenophora pectinicornis


XIV.—RHYPHIDÆ

22. Rhyphos cinctus

[Illustration: PLATE II. (APPENDIX).]


                               PLATE III

_Family Type-Forms of Antennæ in the second section, or Flies with three
                        or few-jointed Antennæ_


XV.—STRATIOMYIDÆ

1. Pachygaster atra

2. Oxycera pulchella

3. Stratiomys chamæleon

4. Sargus cuprarius

5. Beris chalybeata

6. Nemotelus uliginosus


XVI.—TABANIDÆ

7. Chrysops cæcutiens

8. Hæmatopota pluvialis

9. Tabanus bovinus


XVII.—LEPTIDÆ

10. Chrysopilus auratus

11. Leptis scolopacea

12. Atherix ibis

13. Symphoromyia melaena

14. Spania nigra


XVIII.—ASILIDÆ

15. Leptogaster cylindrica

16. Dioctria œlandica

17. Isopogon brevirostris

18. Laphria marginata

19. Asilus crabroniformis


XIX.—BOMBYLIDÆ

20. Anthrax hottentota

21. Bombylius major


XX.—THEREVIDÆ

22. Thereva annulata


XXI.—SCENOPINIDÆ

23. Scenopinus fenestralis


XXIII.—EMPIDÆ

24a. Empis livida

24b. Empis borealis

25. Ardoptera irrorata

26. Ocydromia glabricula

27. Stilpon lunata

28a. Clinocera stagnalis

28b. Clinocera lota

29. Hybos grossipes

30. Tachista arrogans

31. Chersodromia hirta

32. Cyrtoma spuria


XXIV.—DOLICHOPODIDÆ

33. Psilopus wiedemanni

34a. Dolichopus longicornis

34b. Dolichopus discifer

35. Chrysotus gramineus

36. Rhaphium longicorne

37. Medeterus diadema


XXV.—LONCHOPTERIDÆ

38. Lonchoptera lutea


XXVI.—PLATYPEZIDÆ

39. Platycnema pulicaria

40. Platypeza picta


XXVII.—PIPUNCULIDÆ

41. Chalarus spurius

42. Pipunculus campestris


XXVIII.—SYRPHIDÆ

43. Volucella bombylans

44. Xylota sylvarum

45. Orthoneura elegans

46. Chrysotoxum arcuatum


XXIX.—CONOPIDÆ

47. Myopa buccata

48. Physocephala rufipes


XXXI.—TACHINIDÆ

49. Zophomyia temula

50. Sarcophaga carnaria


XXXII.—MUSCIDÆ

51. Calliphora vomitoria


XXXIV.—CORDYLURIDÆ

52. Coniosternum obscurum

53. Scatophaga stercoraria


XXXVIII.—SCIOMYZIDÆ

54. Tetanocera ferruginea


LVI.—BORBORIDÆ

55. Borborus nitidus


XXX.—ŒSTRIDÆ

56. Hypoderma bovis


LVII.—PHORIDÆ

57. Phora incrassata

[Illustration: PLATE III. (APPENDIX).]


                                PLATE IV

              _Family Type-Forms of the Wings of NEMOCERA_


II.—CECIDOMYIDÆ

1. Cecidomyia rosaria

2. Lasioptera rubi

3. Catocha latipes


III.—MYCETOPHILIDÆ

4. Sciara thomæ

5. Mycetophila cingulum

6. Macrocera lutea


IV.—BIBIONIDÆ

7. Bibio pomonæ


V.—SIMULIDÆ

8. Simulium reptans


VI.—CHIRONOMIDÆ

9. Ceratopogon illustris

10. Chironomus plumosus

11. Tanypus monilis


VIII.—PSYCHODIDÆ

12. Psychoda sexpunctata


IX.—CULICIDÆ

13. Culex annulatus


X.—DIXIDÆ

14. Dixa maculata


XI.—PTYCHOPTERIDÆ

15. Ptychoptera contaminata


XIV.—RHYPHIDÆ

16. Rhyphus cinctus


XII.—LIMNOBIDÆ

17. Dicranomyia stigmatica

18. Rhipida maculata

19. Symplecta punctipennis

20. Erioptera fuscipennis

21. Limnophila nemoralis

22. Trichocera hiemalis


XIII.—TIPULIDÆ

23. Nephrotoma dorsalis

24. Dolichopeza sylvicola

25. Pachyrrhina crocata

26. Tipula gigantea

[Illustration: PLATE IV. (APPENDIX).]


                                PLATE V

       _Family Type-Forms of the Wings in the second section, or
                    Flies with few-jointed Antennæ_


XV.—STRATIOMYIDÆ

1. Sargus cuprarius


XVI.—TABANIDÆ

2. Tabanus bovinus


XVII.—LEPTIDÆ

3. Leptis scolopacea


XVIII.—ASILIDÆ

4. Asilus crabroniformis

5. Isopogon brevirostris


XIX.—BOMBYLIDÆ

6. Bombylius major

7. Anthrax hottentota


XX.—THEREVIDÆ

8. Thereva nobilitata


XXI.—SCENOPINIDÆ

9. Scenopinus fenestralis


XXIII.—EMPIDÆ

10. Empis livida

11. Ocydromia glabricula

12. Stilpon lunata


XXII.—CYRTIDÆ

13. Acrocera globulus


XXIV.—DOLICHOPODIDÆ

14. Dolichopus plumipes

15. Medeterus diadema


XXV.—LONCHOPTERIDÆ

16. Lonchoptera lutea, male. The dotted line shows V, 6 in the female.


XXVI.—PLATYPEZIDÆ

17. Platypeza picta


XXVII.—PIPUNCULIDÆ

18. Verralia aucta


XXVIII.—SYRPHIDÆ

19. Syritta pipiens

19-1/2. Eumerus sabulonum

20. Eristalis tenax

21. Brachyopa bicolor


XXIX.—CONOPIDÆ

21-1/2. Physocephala rufipes


XXX.—ŒSTRIDÆ

22. Gastrophilus equi

23. Œstrus ovis


XXXI.—TACHINIDÆ

24. Gymnosoma rotundatum

25. Cercomyia thoracica

26. Dexiosoma caninum

27. Sarcophaga carnaria


XXXII.—MUSCIDÆ

28. Calliphora erythrocephala

29. Mesembrina meridiana


XXXIII.—ANTHOMYIDÆ

30. Anthomyia pluvialis


XXXIV.—CORDYLURIDÆ

31. Scatophaga stercoraria


XXXVIII.—SCIOMYZIDÆ

32. Tetanocera ferruginea


XXXIX.—PSILIDÆ

33. Psila fimentaria


XLII.—TRIPETIDÆ

34. Tephritis corniculata


LVII.—PHORIDÆ

35. Phora rufipes


XL.—MICROPEZIDÆ

36. Micropeza corrigiolata


LI.—CHLOROPIDÆ

37. Centor cereris


LIV.—PHYTOMYZIDÆ

38. Chromatomyia affinis


LVI.—BOBORIDÆ

39. Limosina fontinalis


LVIII.—HIPPOBOSCIDÆ

40. Hippobosca equina

[Illustration: PLATE V. (APPENDIX).]


                                PLATE VI

1. Head of Mycetophila to show the position of the two ocelli.

2. Fore-leg of Dilophus

3. Fore-leg of Bibio

4. Palpus of Limnobia

5. Palpus of Tipula

6. Palpus of Anopheles

7. Palpus of Culex

8. Foot of Dilophus

9. Foot of Leptis

10. Foot of Asilus

11. Foot of Thereva

12. Profile of Eumerus

13. Profile of Syritta

14. Profile of Helophilus

15. Profile of Volucella

16. Profile of Rhingia

17. End of abdomen of Dolichopus 4 (_a_) the forceps (_b_) the pennis
(_c_) the lamellæ

18. Head of Psarus, viewed from above, showing frontal process

19. Shape of the proboscis in Empis

20. Shape of the proboscis in Hilara

21. Shape of the proboscis in Ocydromia

22. Shape of the proboscis in Euthyneura

23. Hind leg of Ramphomyia pennata

24. Hind leg of Sphœrocera subsultans

24-1/2. Palpus of Lispe tentaculata

25. Leg of Limnophila—tibia spurred

26. Leg of Erioptera—tibia not spurred

27. Head and double-jointed proboscis of Myopa

28. Head of Asilus—front view 4 (_a_) the hollowed vertex (_b_) the
mystax

29. Head of Drymia

30. Head and proboscis of Stomoxys calcitrans

31. Dorsum of Culex—no cross-seam

32. Dorsum of Tipula—cross-seams (_a_—_a_), (disregarding characters
other than cross-seams)

33. Dorsum of Muscid (disregarding characters other than cross-seams)

34. Extremity of abdomen of Pedicia rivosa

35. Head of Stenopteryx sunk in shoulders

36. Foot and claws of Hippobosca

37. Puparium of Calliphora

38. T-shaped emergence-orifice in the pupa of Dixa—dorsal aspect

39. A mummy-pupa (Tipula)

40. Diagram of the Dorsum 4 (1-1) Humeri or Shoulders

  (2) Præ-sutural Central Region

  (3) Post-sutural Central Region

  (4-4) Post-humeral Region

  (5-5) Alar Regions

  (6) The Scutellum

  (7) The Neck

  (8) Dorsal Suture

  (9-9) Dorso-pleural Sutures

  (10-10) Wing bases

  (11-11) Scutellar Bridges

  (12-12) The Alar Frena

  (13-13) Inner rows of Dorso-central Bristles

  (14-14) Outer rows of Dorso-central Bristles

  (15) The Scutellar Suture

41. Diagramatic Chætotaxy of an Abdominal Segment 4 (1-1) Side
Fore-marginal bristles

  (2-2) Side Hind-marginal bristles

  (3) Central Fore-marginal bristles

  (4) Central Hind-marginal bristles

  (5) Discal bristles

[Illustration: PLATE VI. (APPENDIX).]


                               PLATE VII

1. Profile of Dorycera graminum

2. Profile of Trigonometopus frontalis

3. Profile of Platystoma seminationis

4. Profile of Ceroxys crassipennis

5. Head of Chilosia maculata ♂

6. Fore-leg of Platychirus manicatus, ♂ (5 should be 6).

7. Fore-leg of Platychirus peltatus, ♂

8. Fore-leg of Platychirus scutatus, ♂

9. Fore-leg of Platychirus albimanus, ♂

10. Fore-leg of Platychirus clypeatus, ♂

11. Platychirus, ♂ and ♀, quadrate spotting

12. Melanostoma mellinum, ♀ triangular spotting

13. Larva of Microdon

14. Wing of Helomyza pallida

15 & 16. Diagram of a fly's leg. _Vide_ C, I, on page 91.

15. As viewed from behind

16. As viewed, horizontal section (through A-B) 4 (_b.f._) base of femur

  (_t.f._) tip of femur

  (_b.t._) base of tibia

  (_t.t._) tip of tibia

  (1) upper or outer side

  (2) under or inner side

  (3) hinder side

  (4) fore side

  (5) upper fore side

  (6) upper hind side

  (7) under hind side

  (8) under fore side

17 & 18. Base of wing, illustrating the difference in O, 6^1
respectively in

17. Urophora

18. Trypeta

19. Profile of Drosophila

20. Profile of Ceratomyza denticornis

21. Profile of Tichomyza fusca

22. Antennæ of Notophila cinerea; note the "thorn" on second joint

23. Antennæ of Hydrellia griseola

24. Antennæ of Tichomyza fusca

25. Profile of Hydrellia griseola

26. Profile of Ochthera mantis

27. Wing of Borborus equinus

28. Wing of Limosina sylvatica

29. Section of a collector's net, showing 4

(_a_) the small end of a large net;

(_b_) a detachable muslin bag;

(_c_) elastic closing the bag;

(_d_) transparent celluloid end

30. A small bag, closed and detached

31. Box for carrying bags

[Illustration: PLATE VII. (APPENDIX).]




                       NUMBERED LIST OF FAMILIES,

     _Together with references to the Analytical Table and Notes._

       The sequence of the numbering indicates some proximity of
 relationship, in most cases at least, in respect of some particulars.


Nos. Refs. FAMILIES—Notes

I —. PULICIDÆ: fleas regarded as flies with atrophied or undeveloped
wings. About 30 native species.

II 3. CECIDOMYIDÆ: mostly gall-gnats, minute and midge-like, or very
frail, slender and gnat-like. _Cecidomyia destructor_ is the notorious
Hessian-fly, injurious to cereal crops.

III 10. MYCETOPHILIDÆ: fungus-gnats; 34 genera; many common species. The
marvellous "army-worm," the larvæ of _Sciara militaris_, which (being
not a feeder on fungi) may be classified either separately or as
belonging to this family, has been observed travelling in Continental
forests in millions, described as massed together with a viscous mucus
in bands said to be as large as 5 or 6 inches wide, 1 inch deep, and 50
or more feet long!

IV 11. BIBIONIDÆ: 40 species of small and medium sizes; commonly the
males are black, but the females of some species coloured; _Bibio
marci_, of a largish size, pubescent, and black, sometimes appears in
great numbers on fine spring days, as likewise do some smaller black
species of the same genus; ocelli absent; semi-blind.

V 13. SIMULIDÆ: midge-like flies, mostly with wings, limbs, and bodies
of short length; the largest, _Simulium reptans_, only 2-3 mm., is
common; its larvæ are aquatic. Some foreign species are called
sand-flies and are much dreaded poisonous blood-suckers.

VI 14. CHIRONOMIDÆ: midges and many small, slender and gnat-like flies;
_Ceratopogon pulicaris_, _C. bipunctatus_, and _C. varius_ are our
commoner native blood-sucking midges, of which the larvæ have been found
under the damp bark of decadent trees; the larvæ of some others are
aquatic, as also are all those of the long slender non-blood-sucking
species, including those of the very common harlequin-fly, _Chironomus
plumosus_, as also of several congerers, including _Ch. dorsalis_, of
which the larvæ are known as "pond blood-worms."

VII 19_b_. ORPHNEPHILIDÆ (darkness-loving): all foreign flies, except
one rare.

VIII 16. PSYCHODIDÆ: minute moth-like flies; they have been named
owl-midges from a peculiar manner of holding their wings in repose.

IX 18. CULICIDÆ: the true gnats or mosquitoes; 5 genera, 18 native
species; three common, including _Culex pipiens_; larvæ abundant about
marshy land and everywhere in water from which _fish are absent_, even
in brackish water, but particularly in the stagnant water of small pools
and vessels.

X 19_a_. DIXIDÆ: a few small and gnat-like flies; larvæ aquatic.

XI 21. PTYCHOPTERIDÆ: larvæ in shallow muddy pools.

XII 23. LIMNOBIDÆ: 32 genera and more than 100 species; generally marsh
and fen slender flies, large and small, rather resembling "crane-flies";
the larvæ live some in decaying vegetable matter, some in fungi, some
are aquatic, and some are unknown; two species called "winter-gnats,"
genus _Trichocera_, are very common.

XIII 24. TIPULIDÆ: true crane-flies or daddy-long-legs; about 60
species; larvæ (leather-jackets) underground in turf, or in decadent
matter.

XIV 8. RHYPHIDÆ: three native species; slender and of medium size; larvæ
in rotting vegetable matter.

XV 28. STRATIOMYIDÆ: 12 genera, 40 or more species; proboscis imperfect;
wings rather small in comparison with the body, which is free from
hairiness; a few are those large and conspicuously bright-coloured
flies, which are called "soldier-flies"; the larvæ of the genus
_Stratiomys_ are known as "star-tailed" maggots.

XVI 30. TABANIDÆ: breeze-flies; ocelli absent; the short well-developed
proboscis of the blood-sucking female pierces the skin of mammalia; the
abdomen is somewhat pubescent, never hairy; semi-blind; larvæ in damp
earth, predaceous.

XVII 31, 37. LEPTIDÆ: a family of few species resembling some Empidæ
rather than the flies of any preceding family. _Leptis scolopacea_ is a
large fly, common in meadows, yellowish body with black spots.

XVIII 40. ASILIDÆ: the "robber-flies," which are more boldly voracious
than any other raptorial flies, preying on winged insects, large and
small; terrestrial predaceous larvæ.

XIX 42. BOMBYLIDÆ: furry, hovering, bee-like flies, mostly very
long-tongued; bodies very rotund but with legs singularly thin; larvæ,
some parasitic on the larvæ of ground bees, some unknown.

XX 43. THEREVIDÆ: non-raptorial flies; smaller, shorter, and more feeble
than Asilidæ; though differing much in wing-pattern superficially like
some Leptidæ or some Empidæ.

XXI 44. SCENOPINIDÆ: a very limited family of smallish flies.
_Scenopinus fenestralis_, the "window-fly" was formerly thought to breed
amidst old carpets and musty neglected clothing, but its larvæ have been
found to be therein predaceous devourers of the larvæ of clothes-moths
and fleas; larvæ of other species feed on fungi.

XXII 38. CYRTIDÆ: quite unlike any of the preceeding or succeeding
families; flies with diminutive heads and large rotund abdomens;
proboscis very short or obsolete; the larvæ of some are said to be
parasitic on spiders.

XXIII 45, 49, 66_a_. EMPIDÆ: an extensive family; about 200 species,
mostly of small sizes; of slender habit, and of dull colours; there are
30 genera and the characteristics of some are peculiar; the life-history
and habits of most are unrecorded; though with bodies of feeble
appearance, some have the proboscis well developed and are predaceous on
small insects. Amongst the most curious are some species of the genus
_Hilara_, of which the males have the first tarsal joint of the fore-leg
thickened and flattened; some species of this genus, not very uncommon,
fly and float about carrying "veils" or small cob-web-like attachments.

XXIV 50, 65. DOLICHOPODIDÆ: long-legged; a large family of 42 genera;
some species of medium size but mostly small, amongst which latter
bright metallic colours, often golden green, are common. The
life-history of only a few is known.

XXV 51. LONCHOPTERIDÆ: a few small slender flies with long pointed
wings.

XXVI 53. PLATYPEZIDÆ: small flies; the peculiar broad flat larvæ of some
of the genus _Platypeza_ have been found in fungi.

XXVII 58. PIPUNCULIDÆ: small and uncommon flies with abnormally large
eyes.

XXVIII 59. SYRPHIDÆ: a most interesting group of 51 genera;
"hover-flies," and other various, conspicuous, large and medium sized
flies (only a few small), very distinctly characterised and
differentiated; the wings show the "vena spuria," and the face is
without a "frontal suture." The larvæ are very diversified; some are
terrestrial, some aquatic, some insectivorous, some parasitic or
commensal in the nests of _Hymenoptera_.

XXIX 54, 60. CONOPIDÆ: the wings show no "vena spuria"; the known larvæ
are parasitic on _Hymenoptera_ and _Orthoptera_.

XXX 62. ŒSTRIDÆ: a few very distinct species; proboscis and mouth parts
atrophied; very hairy except one very rare; parasites of mammalia.

XXXI 72. TACHINIDÆ: 100 genera, more than 250 native species; with great
difficulty classed in divisions, which may rank as separate families;
stoutness of body and abundance of strong hairs, or rather _bristles_,
are so generally apparent that many species may be guessed to belong to
this family rather than to the closely related Muscidæ. Many of the
larvæ are parasitic on various insects.

XXXII 73. MUSCIDÆ: 15 genera, comprising 36 native species, mostly very
common, and many superabundant throughout summer by reason of rapid
breeding.

XXXIII 74. ANTHOMYIDÆ: 4 sub-families (MYDÆINÆ, ANTHOMYINÆ, HOMALOMYINÆ,
CŒNOSINÆ), 36 genera, and nearly 300 native species; difficult to
characterise, but many rather resemble the lesser house-fly in size, and
more or less in appearance, habit, and life-history, but some seem
attracted rather more to flowers and others drawn only towards dung.

XXXIV 82. CORDYLURIDÆ: 29 genera; absence of squamæ apparent; otherwise
generic features and general sizes and bodily shapes of species vary
considerably. The yellow cow-dung fly, _Scatophaga stercoraria_, is the
commonest species of this large family.

XXXV 89, 116. PHYCODROMIDÆ: sea-shore flies.

XXXVI 80. HELOMYZIDÆ: 8 genera; the costa of wings very "pectinate";
wings large and abdomen small.

XXXVII 78. HETERONEURIDÆ: 3 native species; smallish elongated wings;
the larvæ, which live in rotten wood, can jump, somewhat like the
cheese-hopper maggots.

XXXVIII 86, 95. SCIOMYZIDÆ: 11 genera; slender flies with tinted
brownish wings; larvæ aquatic.

XXXIX 101, 135. PSILIDÆ: 4 genera.

XL 103, 109. MICROPEZIDÆ: 6 native species.

XLI 87, 104. ORTALIDÆ: about 20 species; smallish flies; some common in
pastures; legs short and stout.

XLII 97. TRIPETIDÆ: numerous small species; larvæ in stems of plants, or
galls thereon, some leaf-miners.

XLIII 92. LONCHÆIDÆ: some are of a plump figure and a dark metallic blue
or green, others more slender and yellow, grey, or black.

XLIV 93. SAPROMYZIDÆ: 21 species.

XLV 139. OPOMYZIDÆ: 5 species; life-history unknown.

XLVI 83, 102, 121, 136. SEPSIDÆ: several are common small dung-flies,
with black bodies, somewhat ant-like.

XLVII 120. PIOPHILIDÆ: the "cheese-hopper" maggots are larvæ of
_Piophila casei_; seven other species.

XLVIII 132. GEOMYZIDÆ: 12 species.

XLIX 113. EPHYDRIDÆ: nearly 100 species; life-history of few known.

L 114, 131. DROSOPHILIDÆ: larvæ leaf-miners. The pale yellow
"fruit-fly," _Drosophila fenestrarum_, loves the cider-press and
fermenting fruit.

LI 111. CHLOROPIDÆ: numerous family; in the genus _Chlorops_ are many
beautiful little flies.

LII 129. MICHILIDÆ: 2 native species.

LIII 127, 138. AGROMYZIDÆ: some are leaf-miners.

LIV 68, 125. PHYTOMYZIDÆ: leaf-miners.

LV 126. ASTIADÆ: 2 species; life-history unknown.

LVI 106. BORBORIDÆ: first tarsal joint (C, 1, 5) of hind leg
conspicuously thick and short; small species of the genera _Borborus_
and _Spherocera_ often abound in the dung-pits of mews. The larvæ of
some have been found on rotting potatoes and on confervæ.

LVII 140. PHORIDÆ: a numerous family of small flies; 6 genera.

LVIII 144. HIPPOBOSCIDÆ: the females of some shed their wings, and all
live a lice-like life attached to animals.

LIX 143. BRAULIDÆ: eyeless and with strangely atrophied body appendages;
found in bee-hives.

LX 145. NYCTERIBIDÆ: wingless parasites on bats; with small heads held
in a curious posture.




                      ANALYTICAL TABLE OF FAMILIES

                             ORDER—DIPTERA


1 (141). Insects with the head distinct from the thorax, with one pair
of wings, one pair of halteres, 5-jointed tarsi, proboscis not spirally
coiled; with a well defined pupal stage intermediate between the larval
stage and the perfect insect.

1-1/2 (52-1/2). Frontal lunule absent.


SUB-ORDER I. ORTHORRHAPHA (comprising 25 families); flies with
"mummy-pupæ," _see plate_ VI, figs. 38 and 39.

2 (25). Antennæ many-jointed (_plate_ II).


NEMATOCERA (thread-horns)—

3 (4). Vein endings round the margin (_plate_ IV, figs. 1, 2, 3) not
more than 6.


                            CECIDOMYIDÆ, II

4 (3). Vein endings more than 6.

5 (20). Thorax (_plate_ VI, 31) without B, I, 8 conspicuous.

6 (15). Costa ending at apex of wing (_plate_ IV, 4-11).

7 (12). Ocelli as in _plate_ I, or as in _plates_ VI, I and II, 4.

8 (9). Discal cell (O, 4_b_ or O, 5^2) present (_plate_ IV, 16).


                             RHYPHIDÆ, XIV

9 (8). Discal cell absent (_plate_ IV, 4-7).

10 (11). Antennæ long (_plate_ II, 3-6); or, if short, coxæ elongated.


                           MYCETOPHILIDÆ, III

11 (10). Antennæ as in _plate_ II, 7 and 8; coxæ not elongated.


                             BIBIONIDÆ, IV

12 (7). Ocelli absent.

13 (14). Antennæ (_plate_ II, 9) shorter than B; wings (_plate_ IV, 9)
broad.


                              SIMULIDÆ, V

14 (13). Antennæ (_plate_ II, 10, 11) longer; wings narrow (_plate_ IV
9-11).


                            CHIRONOMIDÆ, VI

15 (6). Costa (_plate_ IV, 12-14) around hind margin.

16 (17). Wings held roof-like, hairy; X only at base (_plate_ IV, 12).


                            PSYCHODIDÆ, VIII

17 (16). Wings flat over D; X on middle of wing.

18 (19). Veins hairy (_plate_ IV, 13).


                              CULICIDÆ, IX


19 (18). Veins bare.

19_a_ (19_b_). Antennæ long; V, 4 and V, 2 forked; X, 4 (_plate_ IV, 14)
ending in V, 2.


                               DIXIDÆ, X

19_b_ (19_a_). Antennæ very short but 11-jointed; no veins forked.


                           ORPHNEPHILIDÆ, VII

20 (5). Thorax (_plate_ VI, 32) with a strong cross seam.

21 (22). V, 6 absent (_plate_ IV, 15).


                           PTYCHOPTERIDÆ, XI

22 (21). V, 6 present.

23 (24). V, 1_a_ ending in costa and (_plate_ IV, 17-22) united to V,
1_b_ by X, 1_b_; last joint of palpi (_plate_ VI, 4) never whip-like.


                             LIMNOBIDÆ, XII

24 (23). V, 1_a_ ending in V, 1_b_; and, except for X, 1_a_ at its base,
not united by X (_plate_ IV, 23-26); palpi (_plate_ VI, 5).


                             TIPULIDÆ, XIII

25 (2). Antennæ short, 3-jointed (_plate_ III); 3rd joint sometimes
ringed.


BRACHYCERA (short-horns)—

26 (140). Wing veining normal; X-veins present.

27 (32). Third antennal joint ringed; A, IV, 6, if present (_plate_ III,
1-9) apical.

28 (29). Costa ending at apex of wing (_plate_ V, 1).


                            STRATIOMYIDÆ, XV

29 (28). Costa around the hind margin (_plate_ V, 2).

30 (31). Squamæ very large.


                             TABANIDÆ, XVI

31 (30). Squamæ very small.


               _Part of_ LEPTIDÆ, XVII (genus Xylophagus)

32 (27). Third joint of antennæ (_plate_ III, 10-55) not ringed.

33 (55). Arista terminal or wanting (_plate_ III, 10-26, 28-32, 35-40,
48)

34 (46). V, 3 forked (_plate_ V, 3-10, 13).

35 (45). O, 6^1 long, extending (or nearly) to hind margin, or entirely
wanting (_plate_ V, 3-9, 13).

36 (39). C, I, (II) much enlarged, appearance of 3 foot-pads (_plate_
VI, 9)

37 (38). Squamæ small, not covering C, III; O, 6^1 long and distinct
(_plate_ V, 3); long bodied flies, head of normal proportions.


                        _Part of_ LEPTIDÆ, XVII

38 (37). Squamæ very large, hiding the halteres; O, 6^1 absent (_plate_
V, 13); short round-bodied flies with very small heads.


                             CYRTIDÆ, XXII

39 (36). Empodium small, only 2 foot-pads apparent (_plate_ VI, 10, 11).

40 (41). Vertex hollowed out between the eyes (_plate_ VI, 28).


                             ASILIDÆ, XVIII

41 (40). Vertex flat or raised, eyes not protruding.

42 (43) (44). V, 4 ending in 3 branches (_plate_ V, 6, 7) between V, 3
and V, 5.


                             BOMBYLIDÆ, XIX

43 (42) (44). V, 4 ending in 4 branches (_plate_ V, 8) between V, 3 and
V, 5.


                             THEREVIDÆ, XX

44 (42) (43). V, 4 ending in 2 branches (_plate_ V, 9); antennæ (_plate_
III, 23) without A, IV, 6.


                            SCENOPINIDÆ, XXI

45 (35). O, 6^1 short (_plate_ V, 10) not nearly reaching hind margin.


                        _Part of_ EMPIDÆ, XXIII

46 (34). V, 3 not forked (_plate_ V, 11-12, 14-17).

47 (52). Alulæ absent or rudimentary.

48 (51). Apex of the wing rounded.

49 (50). X, 4 placed generally beyond X, 5^1, at most only a little
before it; V, 5 with 2 X-veins bounding a discal cell (_plate_ V, 11);
or, if only one, then X, 5 is placed before, or, at most (_plate_ V, 12)
only a little beyond X, 4.


                        _Part of_ EMPIDÆ, XXIII

50 (49). X, 4 placed very near the base of the wing; V, 5 with only one
X-vein placed far beyond X, 4; no discal cell (_plate_ V, 14, 15).


                     _Part of_ DOLICHOPODIDÆ, XXIV

51 (48). Apex of the wing (_plate_ V, 16) pointed.


                           LONCHOPTERIDÆ, XXV

52 (47). Alulæ present.

52-1/2 (1-1/2). Frontal lunule (_plate_ VII, 5) present.


SUB-ORDER II. CYCLORRHAPHA (families XXVI—LX); flies which escape from a
puparium, formed of the indurated larval skin, through a circular
orifice made by pushing off its head end (_plate_ VI, 37).


PROBOSCIDEA—

53 (54). Antennæ (_plate_ III, 39, 40) with a long seta or bristle.


                           PLATYPEZIDÆ, XXVI

54 (53). Antennæ (_plate_ III, 48) with a short seta or spine.


                        _Part of_ CONOPIDÆ, XXIX

55 (33). Arista dorsal (_plate_ III, 27, 33, 34, 41-47, 49-55).

56 (61). O, 6^1 long (_plate_ V, 18-21-1/2) extending nearly to hind
margin: D without strong bristles (macrochætæ).

57 (60). Proboscis of moderate length (_plate_ VI, 12-16) generally
retracted.

58 (59). Vena spuria (_plate_ V, 18) absent; A, II very large; O, 4^2
open.


                           PIPUNCULIDÆ, XXVII

59 (58). Vena spuria present (_plate_ V, 19-21); O, 4^2. closed; A, II
moderate.


                            SYRPHIDÆ, XXVIII

60 (57). Proboscis projecting far in front, very thin and long, often
double-kneed (_plate_ VI, 27); no vena spuria (_plate_ V, 21-1/2).


                        _Part of_ CONOPIDÆ, XXIX

61 (56). O, 6^1 short, not nearly reaching margin, or absent (_plate_ V,
12, 22-39) abdomen often with strong bristles.

62 (63). Proboscis and palpi atrophied.


                              ŒSTRIDÆ, XXX

63 (62). A, VIII, 3 and 4 distinctly present.

64 (67). X, 5^1 absent, X 5^2 present, _i.e._, only one X-vein on V, 5
and that beyond X, 4.

65 (66). X, 4 very near base of wing (_plate_ V, 14, 15); X, 5 far
beyond X, 4.


                     _Part of_ DOLICHOPODIDÆ, XXIV

66 (65). X, 4 more towards middle of wing (_plate_ V, 12, 36, 37) nearer
X, 5.

66_a_ (66_b_). Proboscis directed straight downwards.


                _Part of_ EMPIDÆ, XXIII (genus Stilpon)

66_b_ (66_a_). A, VIII, 3 retracted [ordinary Muscid type] pass on to
108 of this table.

67 (64). X, 5^1 present, that is, a X-vein on V, 5 before, or under X,
4; or no X-veins on V, 5.

68 (69). No X-veins on V, 5.


_Part of_ PHYTOMYZIDÆ, LIV

69 (68). At least X, 5^1 present, generally also X, 5^2.

70 (75). Squamæ distinctly present though sometimes small.


MUSCIDÆ CALYPTERÆ—

71 (74). V, 4 angled or bent towards V, 3 (_plate_ V, 24-29).

72 (73). D with E (macrochætæ and hairs) on middle segments; otherwise
A, IV, 6 is bare or bare on the tip-half (_plate_ III, 49-50).


                            TACHINIDÆ, XXXI

73 (72). D without macrochætæ though often with rather strong hairs; A,
IV, 6 fully plumed or combed (_plate_ III, 51).


                             MUSCIDÆ, XXXII

74 (71). V, 4 going straight or nearly straight to margin (_plate_ V,
30).


                           ANTHOMYIDÆ, XXXIII

75 (70). Squamæ absent or rudimentary.


MUSCIDÆ ACALYPTERÆ—

76 (105). V, 1_a_ distinctly present, nearly as thick as V, 1_b_, which
generally ends in the fore margin at or beyond the middle of the wing
(_plate_ V, 31, 32, 34).

77 (84). Vibrissæ present (_plate_ VIII, 2) together with more or less
hair.

78 (79). V, 4^4 four or five times as long as V, 4^3 (_i.e._, X, 5^2
nearer X^4 than to wing margin).


                         HETERONEURIDÆ, XXXVII

79 (78). V, 4^4 about equal to V, 4^3, or only a little longer.

80 (81). Costa with spines in addition to the ciliation (_plate_ VII,
14).


                           HELOMYZIDÆ, XXXVI

81 (80). Costa without a row of spines, only ciliated.

82 (83). A, III (5) present, or, if absent, then body never shining
black.


                           CORDYLURIDÆ, XXXIV

83 (82). Fronto-orbital bristles absent; body always shining black.


                        _Part of_ SEPSIDÆ, XLVI

84 (77). Vibrissæ absent; mouth with short hairs or bare (_plate_ VII,
1, 3, 4); or, if the hairs are strong, all of same length and strength.

85 (88). A, IV very long and horizontal; A, IV (4) as long or longer
than A, IV (5) of which the upper edge is concave (_plates_ III, 54;
VII, 1).

86 (87). Profile not triangular; face perpendicular or slightly
retreating.


                     _Part of_ SCIOMYZIDÆ, XXXVIII

87 (86). Profile triangular; A, V retreating (_plate_ VII, 1) almost
horizontally.


                        _Part of_ ORTALIDÆ, XLI

88 (85). Antennæ not long, or, if long, drooping; A, IV (4) shorter than
A, IV (5) of which the upper edge is straight or convex.

89 (90). Brown or black shore flies with flat horny thorax and with
strong mouth hairs.


                      _Part of_ PHYCODROMIDÆ, XXXV

90 (89). Otherwise than 89.

91 (94). O, 5^1 and O, 6^1 very small and indistinct.

92 (93). Only one fronto-orbital bristle on each side; tibiæ all without
the præ-apical bristle.


                            LONCHÆIDÆ, XLIII

93 (92). A, III (5) on each side; the præ-apical E on some of the C, I
(4).


                           SAPROMYZIDÆ, XLIV

94 (91). O, 5^1 and O, 6^1 fairly large and quite distinct.

95 (96). Hind tibiæ with a præ-apical bristle.


                     _Part of_ SCIOMYZIDÆ, XXXVIII

96 (95). Hind tibiæ without the præ-apical bristle.

97 (98). A, III (6) present and close to A, II; V, 1_a_ sharply bent up
at its end (_plate_ V, 34). Wings usually spotted; ovipositor
protruding.


                            TRYPETIDÆ, XLII

98 (97). Lower fronto-orbital bristles absent; V, 1_a_ gently bent up.

99 (104). Legs long; abdomen narrow and long, contracted at base.

100 (103). V, 4 straight or nearly so. Shining black species.

101 (102). V, 6 reaching to the wing margin; abdomen narrow, more than
twice as long as the thorax.


                        _Part of_ PSILIDÆ, XXXIX

102 (101). V, 6 not nearly reaching margin; D rather broad.


                        _Part of_ SEPSIDÆ, XLVI

103 (100). V, 4 much bent towards V, 3. Brown species.


               _Part of_ MICROPEZIDÆ, XL (genus Calobata)

104 (99). Legs normal; D comparatively short and broad, never contracted
at base.


                        _Part of_ ORTALIDÆ, XLI

105 (76). V, 1_a_ absent or rudimentary, much thinner than V, 1_b_,
which latter ends at or before the middle of the fore margin.

106 (107). Hind C, I (5) thickened and shorter than the next joint.


                             BORBORIDÆ, LVI

107 (106). Hind metatarsus longer than and not thicker than C, I(6).

108 (115). X, 5^1 absent, X, 5^2 present (_i.e._ only one X-vein on V, 5
and that placed beyond X, 4 (_plate_ V, 36).

109 (110). Legs long and thin; abdomen very long.


              _Part of_ MICROPEZIDÆ, XL (genus Micropeza)

110 (109). Legs short and strong; D oval or elliptical.

111 (112). A, III (6) absent; A, IV (5) round, or, if lengthened, then A
in profile is triangular.


                             CHLOROPIDÆ, LI

112 (111). A, III (6) present; A, IV (5) generally long or oval; A in
profile never triangular.

113 (114). Head square; face strongly convex (_plate_ VII, 21); O, 6^1
absent. Not orange coloured species.


                            EPHYDRIDÆ, XLIX

114 (113). Head round or semi-circular; face not arched (_plate_ VII,
19); O, 6^1 present, or, if absent, then the species orange coloured.


                       _Part of_ DROSOPHILIDÆ, L.

115 (108). X, 5^1 present, or, if absent, then X, 5^2 also absent
(_i.e._, either two X-veins or no X-veins on V, 5) (_plate_ V, 33, 38).

116 (117). Scutellum of the male extraordinarily long and squared off
behind; costa thickened from the end of V, 1 to the wing tip.


               _Part of_ PHYCODROMIDÆ (genus Thyreophora)

117 (116). B, I (6) usually short, and somewhat triangular; costa
normal.

118 (133). Mouth bristles present.

119 (122). Fronto-orbital bristles absent.

120 (121). Wings without a black spot near the tip.


                           PIOPHILIDÆ, XLVII

121 (120). Wings with a black spot near the tip.


                        _Part of_ SEPSIDÆ, XLVI

122 (119). Fronto-orbital bristles present.

123 (128). X, 5^2 before middle of wing (both X, 4 and X, 5^2 near the
base and exceedingly near together) or no X-vein on V, 5.

124 (127). X, 5^2 immediately under X, 4 (or nearer the base), or X, 5^1
and X, 5^2 both absent (_plate_ V, 38).

125 (126). Arista bare or nearly so.


                       _Part of_ PHYTOMYZIDÆ, LIV

126 (125). Arista with long hairs on one side.


                              ASTIADÆ, LV

127 (124). X, 5^2 present and placed further from base than X, 4.


                       _Part of_ AGROMYZIDÆ, LIII

128 (123). X, 5^2 at or beyond the middle; X, 4 and X, 5^2 neither very
near to the wing base nor to one another.

129 (130). Arista bare; body short and broad.


                             MILICHIDÆ, LII

130 (129). Arista plumose, combed, or pubescent, or, if bare, then the
body always narrow and long.

131 (132). Arista thinly but long haired, plumose, or combed.


                       _Part of_ DROSOPHILIDÆ, L

132 (131). Arista thickly and short haired, pubescent, or bare.


                           GEOMYZIDÆ, XLVIII

133 (118). Mouth bristles absent.

134 (137). O, 5^1 and O, 6^1 large and very prominent.

135 (136). Antennæ moderately long or very long, male genitalia not
prominent.


                        _Part of_ PSILIDÆ, XXXIX

136 (135). Antennæ short; male genitalia prominent, and club-shaped.


                _Part of_ SEPSIDÆ, XLVI (genus Tetanura)

137 (134). O, 5^1 and O, 6^1 small and not very prominent.

138 (139). Light grey or silvery species.


                       _Part of_ AGROMYZIDÆ, LIII

139 (138). Orange or brownish-red species.


                        _Part of_ OPOMYZIDÆ, XLV

140 (26). Wings with two short very thick veins (in fore-basal region)
whence spring a few very fine unbranched veins. X-veins absent (_plate_
V, 35).


                             PHORIDÆ, LVII

141 (1) (52-3/4). Body of a horny or leathery nature; head sunk into a
hollow in the thorax (_plate_ VI, 35). No proper proboscis or palpi;
claws very large (_plate_ VI, 36). Perfect insect parasitic.


EPROBOSCIDEA—

142 (145). Head fairly large; wings sometimes shed or absent.

143 (144). Eyes, ocelli, scutellum, halteres, and wings all absent; last
tarsal joint combed with bristles.


                             BRAULIDÆ, LIX

144 (143). Eyes and scutellum present; last tarsal joint with well
developed claws.


                          HIPPOBOSCIDÆ, LVIII

145 (142). Head small, when at rest thrown back upon the dorsum; always
wingless.


                            NYCTERIBIDÆ, LX




                                 INDEX


 Air-sacks, breathing by, 46

 ANTHOMYIDA, 10, 17

 _Asilus crabroniformis_, 55

 Aphides, plant-lice, etc., 8


 Beelzebub, Lord-of-flies, 2

 BIBIONIDÆ, semi-blindness of, 108

 Birds, food for, 80

 Black death, 2

 Blood-sucking flies, kinds of—
   genus, _chrysops_, 24
   genus, _hæmatobia_, 16
   genus, _hæmatopota_, 23
   genus, _lyperosia_, 17
   genus, _tabanus_, 23
   genus, _therioplectes_, 23

 Blood-sucking midges and gnats
   —common species—
   _ceratopogon pulicaris_, 108
   _ceratopogon bipunctatus_, 108

 _ceratopogon varius_, 108
   (also others of the same genus and of the allied genus, _anopheles_)
   _culex pipiens_, 108

 Blue-bottles, 12, 18, 33, 36, 51

 _Borborus equinus_, 34

 Bot-fly of the horse, 26

 Breeze-flies, "blinden," 10, 23, 29, 69

 Bridgewater Treatises, 1


 Cabbage-fly, 17

 _Calliphora erythrocephala_ } _see_ blue-bottles

 _Calliphora vomitoria_ } _see_ blue-bottles

 Celery-fly, 17

 Chelifers, 55

 _Chrysops cæcutiens_, 24
 _Chrysops relicta_, 24

 _Conops flavipes_, 22

 Contagion, fly-borne, 84

 CORDYLURIDA, 10

 Cow-dung fly, the yellow, 19

 Crane-flies, or Daddy-long-legs, 109

 Cremation of refuse, 41, 61, 65, 70

 _Cyrtoneura simplex_, 17


 DIPTERÆ, nearly 3,000 species, 10

 Dragon-flies, 55

 Drone-flies, 20, 22

 Dun-flies, _see_ Gad-flies

 Dust-bins, preferably open, 65, 70

 Dust destructor furnace, imperative, 65


 Economic value of the fly, 41

 Egg-traps, domestic refuse as, 65, 72

 EMPIDÆ, 54

 _Empusa muscæ_, 56

 _Eristalis tenax_, 21

 Exclusion from rooms, 76


 _Fannia canicularis_, 7
 _Fannia scalaris_, 14, 18

 Filth-flies, 51

 Fleas, 108

 Flecked flesh, 29

 Fly chart, the Wingate, 88

 Fly-traps, 66

 Forest (or spider) fly, 22

 Fungus-flies, 51

 Futurist's Credo, 39


 Gad-flies, 23

 Garden pests, vegetarian, 17

 Gargantuan jokes, 32

 _Gastrophilus_, _see Œstrus_

 Gentles, apparatus for breeding, 80

 Gentles, green, 82

 _Glossina morsitans_, 62

 Green-bottle flies, 20

 Grey blow-flies, 19


 _Hæmatobia stimulans_, 16

 _Hæmatopota crassicornis_, 23
 _Hæmatopota italica_, 23
 _Hæmatopota pluvialis_, 23

 Hibernation, 15, 80

 HIPPOBOSCIDÆ, 22

 Horse-flies, _see_ Forest-flies

 House-fly fungus, 56

 House-fly, larva of, 35

 House-fly, wing pattern of, 12

 Hover-flies, 20

 Human intestinal myiasis, 25, 26

 Humble Creatures, 1, 34
   _hydrotæa dentipes_, 17
   _hydrotæa irritans_, 17


 Instar, pupa, or chrysalid, 40


 Larvæ, _see_ Maggots

 Lesser house-fly, larva of, 36
 Lesser house-fly, wing pattern, 12

 Louse-fly, tick, or ked, 22

 _Lucilia Cæsar_, 20
 _Lucilia sericata_, 20

 _Lyperosia irritans_, 17


 Maggots, feeding in company, 36
 Maggots, insectivorous, 21
 Maggots, jumping or hopping, 111, 112
 Maggots, myiasic possibilities, 28, 37, 82
 Maggots, parasitic on _lepidoptera_, etc., 111
 Maggots, predaceous, 109
 Maggots, "rat-tail," 21
 Maggots, "star-tail," 109

 Meal-worms, 80

 _Merodon narcissi_, 21

 Messengers of peril, 78

 Metamorphosis, 37

 MICRODON, 22

 _Musca corvina_, 14, 17

 _Muscina stabulans_, 18, 27


 Nostril-fly of the sheep, 4, 26, 28


 Ocelli, visual importance of, 45

 Odour of humanity, attracted by, 33

 Œstrid flies, egg-laying aggressions, 31, 69

 _Œstrus hominis_, discredited, 28

 _Œstrus (Gastrophilus) equi_, 27

 _Œstrus (Gastrophilus) hæmorrhoidalis_, 26

 _Œstrus nasalis_ 4

 _Œstrus ovis_, 28
 (_Œstrus ovis hypoderma_) _bovis_, _see_ worble-flies
 (_Œstrus ovis hypoderma_) _lineatum_, _see_ worble-flies

 Onion-fly, 17

 Owl-midges, moth-like, 109


 Pestering flies, commoner kinds of—
   _cyrtoneura simplex_, 17
   _fannia canicularis_, 7
   _fannia scalaris_, 18
   _musca domestica_, 7
   _musca corvina_, 17
   _muscina stabulans_, 18
   and other ANTHOMYIDÆ

 Poisons, effective insecticide, 73

 _Polietes lardaria_, 18

 Pond blood-worms, 108


 Robber-flies, 54, 109

 Root-fly, the, 17


 _Sarcophaga carnaria_, 19

 _Scatophaga stercoraria_, 19

 Scavenging services, 78

 _Scenopinus fenestralis_, 110

 Sex differentiation, 45

 Soldier-flies, 22, 109

 Spiders, flies parasitic on, 110

 Stable-fly, 12, 13, 16, 51

 Stable manure, 67

 _Stomoxys calcitrans_, 12, 13, 16, 51

 STRATIOMYIDÆ, 22, 109

 Swallow, attracted to breed, 53

 Syrphidæ, 20

 _Syrphus_, 21


 TABANIDÆ, 10, 22, _see also_ blood-sucking flies

 TACHINIDÆ, 10, 19

 _Therioplectes_, _see_ blood-sucking flies

 TIPULIDÆ, 109

 Traps for flies, some ineffective, 72

 Turnip-fly, a beetle, 17


 Veins of wings, 11

 Voltairean atheism, controversy of, 5

 VOLUCELLA, 21


 Warning signals, flies as, 78

 Westminster Hospital and myiasis, 28

 Window-fly, the, 110

 Window screens, 77

 Wingate's nomenclature symbols, 12

 Wing patterns contrasted, 12

 Worble-flies, 26, 28, 69

                WOODS & SONS LTD., PRINTERS, LONDON, N.




Transcribers note.


This work is presented as is, with no changes to the spelling, except
for confirmed typos. Printer's errors, where obvious, and original
spelling have been retained.

Variations in hyphenation and compound words have been preserved.

Italicized words and phrases in the text version are presented by
surrounding the text with underscores.

The Caret character (^) is used to denote superscripts.

Table of Contents, List of Illustrations, etc. Discrepancies: many of
the items in the front matter sections do not match the titles in the
book's content section.





End of Project Gutenberg's The Book of the Fly, by G. Hurlstone Hardy