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THE BRITISH WOODLICE.




This monograph first appeared in the "Essex Naturalist" (Volume XIV.,
1905-6) and has been republished by special arrangement with the
Council of the Essex Field Club.




THE BRITISH WOODLICE.

BEING

A MONOGRAPH OF THE TERRESTRIAL ISOPOD CRUSTACEA

OCCURRING IN THE BRITISH ISLANDS.

BY

WILFRED MARK WEBB, F.L.S.,

_Lecturer on Biology and Nature Study to the Surrey County Council,
Honorary Secretary of the Selborne Society, Sometime, Senior Assistant
Lecturer on Biology to the Essex County Council, and Editor of the
Journal of Malacology, Joint Author of_ "Eton Nature Study and
Observational Lessons."

AND

CHARLES SILLEM.

WITH TWENTY-FIVE PLATES AND FIFTY-NINE FIGURES IN THE TEXT.

  LONDON:
  DUCKWORTH & CO.,
  3, HENRIETTA STREET, COVENT GARDEN.
  1906.




PREFACE.


In Professor Sars' "Crustacea of Norway," quite a number of the British
species of woodlice are figured in detail and described in English, but
few copies of this fine work are to be met with in our country. The
Rev. Canon Norman has from time to time published notes on the British
species in "The Annals and Magazine of Natural History;" these are,
however, scattered, and contain but few figures, while other literature
that exists is out of date. Under these circumstances, we have thought
that the following account and figures of all the British species would
be useful to those anxious to work at the woodlice, and might also
encourage others to pay attention to the distribution and habits of the
interesting tribe to which they belong.

The writers would welcome any corrections or additions in view of a
second edition.

    W.M.W.
    C.S.

ODSTOCK, HANWELL, _December, 1905_.




CONTENTS.


                                                                 PAGE

  Introduction                                                     1
  Geological history                                               1
  External structure and appendages                                2
  Alimentary canal                                                 6
  Circulatory system                                               7
  Excretory system                                                 7
  Nervous system                                                   8
  Reproductive organs                                              8
  Development                                                      9
  Habits and Economic considerations                               12
  Local names                                                      15
  Methods of collections and preservation                          16
  Classification                                                   17
  Scheme of classification and synopsis of generic characters      18
  British Species                                                  19
  Section--Ligiæ                                                   19
  Family--Ligiidæ                                                  19
  Genus--Ligia Fabricius                                           19
  _Ligia oceanica_ Linzé                                           19
  Genus--Ligidium Brandt                                           21
  _Ligidium hypnorum_ Cuvier                                       21
  Family--Trichoniscidæ                                            22
  Genus--Trichoniscus Brandt                                       22
  _Trichoniscus pusillus_ Brandt                                   22
  _Trichoniscus vividus_ Koch                                      23
  _Trichoniscus roseus_ Koch                                       24
  Genus--Trichoniscoides, Sars                                     25
  _Trichoniscoides albidus_ Budde-Lund                             25
  Genus--Haplophthalmus Schobl                                     26
  _Haplophthalmus mengii_ Zaddach                                  26
  _Haplophthalmus danicus_ Budde-Lund                              27
  Family--Oniscidæ                                                 27
  Genus--Oniscus Linné                                             27
  _Oniscus asellus_ Linné                                          27
  Genus--Philoscia Latreille                                       29
  _Philoscia muscorum_ Scopoli                                     29
  _Philoscia couchii_ Kinahan                                      30
  Genus--Platyarthrus Brandt                                       30
  _Platyarthrus hoffmannseggii_ Brandt                             30
  Genus--Porcellio Latreille                                       32
  _Porcellio scaber_ Latreille                                     32
  _Porcellio pictus_ Brandt and Ratzeburg                          33
  _Porcellio dilatatus_ Brandt                                     33
  _Porcellio rathkei_ Brandt                                       34
  _Porcellio laevis_ Latreille                                     35
  _Porcellio ratzeburgii_ Brandt                                   36
  Genus--Metoponorthus Budde-Lund                                  37
  _Metoponorthus pruinosus_ Brandt                                 37
  _Metoponorthus cingendus_ Kinahan                                38
  Genus--Cylisticus Schnitzler                                     38
  _Cylisticus convexus_ De Geer                                    39
  Family--Armadillidiidæ                                           40
  Genus--Armadillidium Brandt                                      40
  _Armadillidium nasatum_ Budde-Lund                               40
  _Armadillidium vulgare_ Latreille                                41
  _Armadillidium pulchellum_ Zencker                               42
  _Armadillidium depressum_ Brandt                                 43
  Distribution of species                                          43
  Conclusion                                                       43
  Bibliography                                                     49




LIST OF FIGURES.


PLATES I.-XXV. with a List, will be found at the end of the Book.


FIGURE.                                                          PAGE.

  1. Parts of the body (_Oniscus asellus_)                         2
  2. The first antenna (_Oniscus asellus_)                         2
  3. The second antenna (_Oniscus asellus_)                        3
  4. The underside of the head (_Oniscus asellus_)                 3
  5. The mandibles (_Oniscus asellus_)                             4
  6. The first maxillae (_Oniscus asellus_)                        4
  7. The second maxillae (_Oniscus asellus_)                       4
  8. The fused maxillipeds (_Oniscus asellus_)                     4
  9. The "upper lip" (_Oniscus asellus_)                           5
  10. The "lower lip" (_Oniscus asellus_)                          5
  11. A typical thoracic segment (_Oniscus asellus_)               5
  12. The fifth thoracic segment of a female
        (_Oniscus asellus_)                                        5
  13. The underside of the abdomen of a female
        (_Oniscus asellus_)                                        6
  14. A typical abdominal appendage
        (_Oniscus asellus_)                                        6
  15. The first abdominal appendage of the male
        (_Oniscus asellus_)                                        6
  16. The second abdominal appendage of the male
        (_Oniscus asellus_)                                        6
  17. The alimentary canal (_Oniscus asellus_)                     7
  18. The circulatory system (_Oniscus asellus_)                   7
  19. The nervous system (_Oniscus asellus_)                       8
  20. Female reproductory organs (_Oniscus asellus_)               8
  21. The male reproductory organs (_Oniscus asellus_)             9
  22. The fertilized egg (_Porcellio scaber_) after Roule         10
  23. The fertilized egg seen in section
        (_Porcellio scaber_) after Roule                          10
  24 to 31. The development of a woodlouse
        (_Porcellio scaber_) after Roule                          10
  32. Embryo of the woodlouse showing the three divisions of the
        intestine separately developed (_Porcellio scaber_)
        after Roule                                               11
  33. Embryo of the woodlouse showing traces of the segments
        (_Porcellio scaber_) after Roule                          11
  34. An embryo woodlouse ready to be hatched
        (_Porcellio scaber_) after Roule                          11
  35. Flagellum and last peduncular joint of the antenna of
        _Ligia oceanica_                                          12
  36. Flagellum and last peduncular joint of the antenna of
        _Ligidium hypnorum_                                       13
  37. Flagellum and last peduncular joint of the antenna of
        _Trichoniscus pusillus_                                   23
  38. Flagellum and last peduncular joint of the antenna of
        _Trichoniscus vividus_                                    24
  39. Flagellum and last peduncular joint of the antenna of
        _Trichoniscus roseus_                                     24
  40. Flagellum and last peduncular joint of the antenna of
        _Trischoniscoides albidus_                                25
  41. Flagellum and last peduncular joint of the antenna of
        _Haplophthalmus mengii_                                   26
  42. Flagellum and last peduncular joint of the antenna of
        _Haplophthalmus danicus_                                  27
  43. Flagellum and last peduncular joint of the antenna of
        _Oniscus asellus_                                         28
  44. Flagellum and last peduncular joint of the antenna of
        _Philoscia muscorum_                                      29
  45. Flagellum and last peduncular joint of the antenna of
        _Philoscia couchii_                                       30
  46. Flagellum and last peduncular joint of the antenna of
        _Platyarthrus hoffmannseggii_                             31
  47. Flagellum and last peduncular joint of the antenna of
        _Porcellio scaber_                                        32
  48. Flagellum and last peduncular joint of the antenna of
        _Porcellio pictus_                                        33
  49. Flagellum and last peduncular joint of the antenna of
        _Porcellio dilatatus_                                     34
  50. Flagellum and last peduncular joint of the antenna of
        _Porcellio rathkei_                                       35
  51. Flagellum and last peduncular joint of the antenna of
        _Porcellio laevis_                                        35
  52. Flagellum and last peduncular joint of the antenna of
        _Porcellio ratzeburgii_                                   36
  53. Flagellum and last peduncular joint of the antenna of
        _Metoponorthus pruinosus_                                 37
  54. Flagellum and last peduncular joint of the antenna of
        _Metoponorthus cingendus_                                 38
  55. Flagellum and last peduncular joint of the antenna of
        _Cylisticus convexus_                                     39
  56. Flagellum and last peduncular joint of the antenna of
        _Armadillidium nasatum_                                   40
  57. Flagellum and last peduncular joint of the antenna of
        _Armadillidium vulgare_                                   41
  58. Flagellum and last peduncular joint of the antenna of
        _Armadillidium pulchellum_                                42
  59. Flagellum and last peduncular joint of the antenna of
        _Armadillidium depressum_                                 43




THE BRITISH WOODLICE.


=Introduction.=--Having finished a somewhat exhaustive list of the land
and fresh-water molluscs of Essex,[1] one of the present writers felt
that if he were to make any further contributions of importance to a
knowledge of the fauna of that interesting county, he must turn his
attention to some other group of animals. It seemed most fitting that
some creatures should be chosen which are commonly met with during the
search for molluscs. Centipedes, millepedes, and woodlice fulfilled
these conditions, and all were collected, but as only seventeen
species of woodlice had at the time been found in England, it was
deemed advisable to study these in detail to begin with. The present
contribution is the result of the undertaking, and we have thought that
a general consideration of the British Woodlice, with careful drawings
from nature of all the species now known from this country, ought to
lead to a more general study of these interesting creatures and their
habits.

=Position in the scheme of classification.=--The Woodlice belong to
an immense group of invertebrate animals known as the Arthropoda, the
bodies of which are segmented and provided with jointed appendages for
purposes of walking, swimming, and feeding. Of this group, two large
divisions are recognized. The first contains the forms which breathe
by means of air-tubes, such as the Insects; and the second has been
constituted for Crustacea, which breathe by means of gills. The latter
are, of course, adapted more especially for a life in water, but here
and there we come across examples so modified that they can exist in
air. The land-crabs are a case in point, and so are the Woodlice. These
belong to an order which contains many fresh-water and marine species,
known as the Isopoda.

=Geological history.=--The known history of the order is a long one,
for remains occur in the Old Red Sandstone (Devonian) of Herefordshire,
and in the Coal Measures. (79)[2]. A form which has been named
_Archæoniscus brodiei_, and is said to be referable to the recent
family Aegidae which is found in some numbers in the Purbeck Beds
(Upper Jurassic), of this country (47). Fossil Isopods have also been
recorded from the Oolite and from the Oligocene (Isle of Wight).

Turning to the Woodlice proper, we find that they first make their
appearance in the Miocene (of Oenigen and Baden), and occur also
in amber (79); while examples of genera, such as _Oniscus_ and
_Porcellio_, have been discovered in late Tertiary deposits (47).

=External structure and appendages.=--Woodlice agree in being of a
somewhat oval form, and their bodies are arched, the curve varying in
different genera and species. A _head_ is to be distinguished; behind
this comes the _thorax_ of seven segments which are often considerably
broader than the six succeeding ones which form the _abdomen_ (see fig.
1.)

[Illustration: FIG. 1.--PARTS OF THE BODY. (_Oniscus asellus._)]

The head carries two _large antennae_ (fig. 3) which are very evident,
and a careful search with a lens will reveal a second and minute pair
(the _smaller antennae_) situated between the base of the others, and
really anterior to them. (figs. 2 and 4.)

[Illustration: FIG. 2.--THE FIRST ANTENNA. (_Oniscus asellus._)]

The larger antennae are customarily bent at certain points, and we can
distinguish a terminal part, or _flagellum_, and a basal part, the
_peduncle_ (fig. 3). The number of joints in these structures, which
varies in different genera and species, forms a useful classificatory
character, and the relative length of the component parts is of
considerable value in distinguishing species.

[Illustration: FIG. 3.--THE SECOND ANTENNA. (_Oniscus asellus._)]

There are four pairs of mouth appendages--namely the jaws or
_mandibles_ (fig. 5), the _first maxillae_ (fig. 6), the _second
maxilla_ (fig. 7), and the _maxillipeds_ (fig. 8). When the head is
examined from the underside the last of these organs will be seen
first, covering in the others.

[Illustration: FIG. 4.--THE UNDERSIDE OF THE HEAD. (_Oniscus
asellus._)]

A small median plate attached to the front of the head has been called
"_the upper lip_" (fig. 9), while inside the mouth appendages is a
little bilobed structure "_the lower lip_" (fig. 10).

[Illustration: FIG. 5.--THE MANDIBLES. (_Oniscus asellus._)]

Before leaving the external features of the head, we must allude to
the pair of _eyes_ which are usually present, though never raised on
stalks. In the Common Woodlouse (_Oniscus asellus_, from which all
our figures to illustrate structure have been made), as in many other
species, the eyes are compound (fig. 4), but in some forms these are
simple.

[Illustration: FIG. 6.--THE FIRST MAXILLAE. (_Oniscus asellus._)]

[Illustration: FIG. 7.--THE SECOND MAXILLAE. (_Oniscus asellus._)]

[Illustration: FIG. 8.--THE FUSED MAXILLIPEDS. (_Oniscus asellus._)]

Each of the seven joints of the thorax bears a pair of _walking legs_
(fig. 11), and in the female at the time when the eggs are laid, a pair
of plates (fig. 12) arises on segments II. to V. These plates together
form a brood pouch, in which the eggs are carried (fig. 12) until
they are hatched, and in which the young ones remain for some time
afterwards.

When we examine the abdomen, we find that the appendages are
plate-like, with the exception of the last pair (fig. 13), and they all
agree in having two divisions, an arrangement which would prove awkward
in limbs used for walking or feeling.

[Illustration: FIG. 9.--THE "UPPER LIP." (_Oniscus asellus._)]

[Illustration: FIG. 10.--THE "LOWER LIP." (_Oniscus asellus._)]

[Illustration: FIG. 11.--A TYPICAL THORACIC SEGMENT. (_Oniscus
asellus._)]

[Illustration: FIG. 12.--THE FIFTH THORACIC SEGMENT OF A FEMALE.
(_Oniscus asellus._)]

The inner plate (or endopodite) is in structure a _gill_, but the blood
that passes through it, is enabled to take up oxygen from moist air,
while the outer division (or exopodite) acts as a protecting cover
(fig. 14). In _Porcellio_, air-tubes (_tracheae_) may be present (see
below).

[Illustration: FIG. 13.--THE UNDERSIDE OF THE ABDOMEN OF A FEMALE.
(_Oniscus asellus._)]

In the male, the first two pairs of abdominal appendages are specially
modified, the inner divisions (endopodites) being long and pointed
(figs. 15 and 16). The last pair, or tail appendages, in the male are
often considerably larger than in the female, and the form of these
structures is sometimes of value in classification.

[Illustration: FIG. 14.--A TYPICAL ABDOMINAL APPENDAGE. (_Oniscus
asellus._)]

[Illustration: FIG. 15.--THE FIRST ABDOMINAL APPENDAGE OF THE MALE.
(_Oniscus asellus._)]

[Illustration: FIG. 16.--THE SECOND ABDOMINAL APPENDAGE OF THE MALE.
(_Oniscus asellus._)]

=Alimentary canal.=--The main portion of the alimentary system is,
practically speaking, a straight tube (fig. 17). Its first part (not
shown in the figure) is a narrow gullet, which after passing through
the nerve collar dilates to form a sort of stomach. Into this the
secretion of four digestive glands is poured by two ducts. These glands
have a somewhat striking appearance, being yellow tubes spirally
coiled, and they end blindly. From the stomach the intestine runs to
the hinder end of the body and passes under the heart.

=Circulatory system.=--The blood being aërated in the abdominal
appendages, we find that the heart is situated towards the hinder end
of the body (fig. 18). Three main arteries supply the thorax and head,
while the blood is brought from the gills to the heart.

=Excretory system.=--The excretory organs consist of a (_a_) pair of
so-called "shell glands," which are considered to be the equivalents
of the excretory tubes or nephridia of annelid worms. In the woodlouse
these excretory organs open on the second pair of maxillae. They are
composed of a tube (_sacculus_) closed at one end and more or less bent
upon itself (5, p. 261) which communicates with a _labyrinth_ that
is provided with an excretory orifice. Matters are eliminated by the
_epithelial cells_ [the histology has been described and figured in
_Ligidium hypnorum_ (66)], which are very large in _Ligia oceanica_.

[Illustration: Fig. 17.--THE ALIMENTARY CANAL. (_Oniscus asellus._)]

[Illustration: Fig. 18.--THE CIRCULATORY SYSTEM. (_Oniscus asellus._)]

(_b_) Masses of cellules in the head, very greatly developed in _Ligia
oceanica_ (but numbering scarcely more than ten in _Oniscus asellus_),
which have no external opening. They also function as excretory organs
(5, p. 263), and have been called "cephalic nephrocytes."

[Illustration: FIG. 19.--THE NERVOUS SYSTEM. (_Oniscus asellus._)]

(_c_) Other "branchial nephrocytes" are situated on the dorsal surface
between the last thoracic and the first abdominal segments, as well as
between those that follow, with the exception of the last two; they are
in distinct patches, one on each of the middle line in _Ligia_, but
more or less continuous in _Oniscus_ (5, p. 265).

(_d_) The digestive glands have also been shown to be excretory (5, p.
270).

=Nervous system.=--The nervous system consists of _paired ganglia_
in the head, above the alimentary canal which send off nerves
(_commissures_) that meet below, to form a _double nerve cord_ with
ganglia at intervals (see fig. 19).

[Illustration: FIG. 20.--FEMALE REPRODUCTORY ORGANS. (_Oniscus
asellus._)]

=Reproductive organs.=--In the female there are a pair of _ovaries_ in
the positions shewn in fig. 20; and _ducts_ run to the underside of the
fifth thoracic segment.

The openings are very difficult to identify, and Lereboullet (39, p.
113) was unable to find them. It is obvious that the openings must be
underneath the plates that form the egg pouch, and as a change of skin
is required to set these free, it would appear that at ordinary seasons
the ducts from the ovaries are closed. The writers have been able to
determine from external examination of specimens which had moulted and
were about to lay eggs, that the oviducts at such time open to the
inside of the base of each walking leg on the fifth segment. In similar
specimens the oviducts were also followed to the opening from within.
The _brood pouch_ has already been described.

The male organs consist of six _testes_ arranged in two pairs, each
of which is provided with a _reservoir_ (see fig. 21). The efferent
ducts from the two reservoirs unite at the base of the thorax to form a
common duct (or "penis").

[Illustration: FIG. 21.--THE MALE REPRODUCTORY ORGANS. (_Oniscus
asellus._)]

=Development.=--The eggs, in the common species of woodlice, at
least, are laid at the beginning of summer, and are retained in the
brood pouch, where they undergo their development. The process has
been recently traced with great care by Professor Louis Roule (58) in
_Porcellio scaber_ and the description which follows is based upon his
researches.

As, practically speaking, the larval stages are passed within the egg,
and there is no free embryo differing in form from the parent, it is
necessary for the young creatures to be well supplied with nutritive
material. In fact, the bulk of the large egg is made up of _food-yolk_,
on the outside of which the _formative protoplasm_ is disposed in
irregular patches. In the fertilized ovum, one of the latter, which
lies in a particular position at the end, is found to be larger than
the others (see fig. 22). It contains the nucleus of the egg-cell (see
fig. 23) and is called the _cicatricula_. This is the only portion of
the egg which divides and produces _nucleated cells_. It is these which
gradually spread all over the surface of the food-yolk, forming a layer
known as the _blastoderm_, which is at first but one cell thick (see
figs. 24, 26, and 28).

Before, however, the food-yolk is quite closed in, a differentiation
into two layers--the _pro-ectoderm_ and _pro-endoderm_--takes place
(see fig. 25) and rudiments of the first two pairs of _appendages_
appear (see fig. 26). Moreover, the cells of the ectoderm change their
shape and begin to multiply at two points to form the beginnings of the
cerebral ganglia and the nerve cord respectively.

[Illustration: FIG. 22.--THE FERTILIZED EGG (_Porcellio scaber_), AFTER
ROULE.]

[Illustration: FIG. 23.--THE FERTILIZED EGG SEEN IN SECTION (_Porcellio
scaber_), AFTER ROULE.]

As the blastoderm closes over the food-yolk, two more appendages arise
and these are soon followed by others (see fig. 28). A depression
appears at the point where the blastoderm closed and internally the
pro-endoderm or inner layer is differentiated into two--the _endoderm
proper_ and the _mesoderm_ (see fig. 29). The former begins to grow
so that its edges unite to form the middle part of the intestine (see
fig. 29) seen from the outside in fig. 30. The depression already
mentioned grows deeper, forming a tube which is the hind portion of the
_intestine_, while at the anterior end of the embryo the front part of
the intestine is similarly formed (see fig. 30). By this time also all
the nineteen appendages have made their appearance and the mesoderm,
(which has grown considerably, to form the beginnings of the muscles)
has sent prolongations into each of them. About this time, spaces (see
fig. 31) are formed in the muscular mesoderm which are all that remain
of the _true body cavity_ characteristic of animals above the level of
the jelly fish, and in these spaces the blood ultimately circulates.

_SURFACE VIEWS._

[Illustration: FIG. 24.]

[Illustration: FIG. 26.]

[Illustration: FIG. 28.]

[Illustration: FIG. 30.]

_OPTICAL SECTIONS._

[Illustration: FIG. 25.]

[Illustration: FIG. 27.]

[Illustration: FIG. 29.]

[Illustration: FIG. 31.]

THE DEVELOPMENT OF A WOODLOUSE (_Porcellio scaber_), AFTER ROULE.

Figs. 24, 26, 28, 30, are Surface Views, and figs. 25, 27, 29, 31,
which indicate slightly later stages respectively than the others, are
of egg seen in Optical Section.

The body next alters somewhat in shape and the three divisions of
the intestine approach one another (see fig. 32) previous to their
junction. As may be imagined during these processes the food-yolk has
gradually been used up and the space which it occupied taken by the
internal organs, which we have mentioned.

[Illustration: FIG. 32.--EMBRYO OF THE WOODLOUSE SHOWING THE THREE
DIVISIONS OF THE INTESTINE SEPARATELY DEVELOPED (_Porcellio scaber_),
AFTER ROULE.]

[Illustration: FIG. 33.--EMBRYO OF THE WOODLOUSE SHOWING TRACES OF THE
SEGMENTS (_Porcellio scaber_), AFTER ROULE.]

[Illustration: FIG. 34.--AN EMBRYO WOODLOUSE READY TO BE HATCHED
(_Porcellio scaber_), AFTER ROULE.]

In the last stages of the development the appendages become larger
still, the _heart_ makes its appearance, segmentation of the body is
completed, and except that the seventh pair of walking legs are as yet
rudimentary the woodlouse is completed. It is only after hatching that
the pair of legs mentioned, attain to their normal length.

The process of segmentation of the egg and the formation of its layers
lasts about a fortnight, while the completion of the development
proceeds much more rapidly, for another three weeks bring it to an end.

After the first moult or change of skin the last pair of walking
legs makes its appearance, and Mr. James B. Casserley [whose work
one of us (75) has described elsewhere] found when keeping a number
of the common pill-woodlouse (_Armadillidium vulgare_) in captivity
that his specimens did not subsequently change their skins more than
once in the six months during which he had them under observation. He
also noted that the crustaceans go on growing after they are sexually
mature. As his specimens grew older, Mr. Casserley noticed that their
colour became darker, and a curious point recorded by him is that two
examples of the same age may change their skins at the same time,
and while one may have afterwards nearly twice as many markings, on
the other very few at all will be seen. The time required for the
growth of a woodlouse from the size of a pin's head to that of an
adult example--say three-quarters-of-an-inch long--must be fairly
considerable, taking into account the fact that any appreciable
increase in size can only occur at a moult and Mr. Casserley's
observations as to the infrequency of the process in _Armadillidium
vulgare_. (See p. 14.)

=Habits and Economic Considerations.=--The construction of the
breathing organs of woodlice, and the necessity which exists for these
to be kept moist, restricts the habitats of the animals considerably.
Woodlice are found under stones and logs, beneath the bark of dead and
rotten trees, among decaying vegetable matter as well as living grass
and moss in damp or wet situations. When looking for some of the common
species under the bark of fallen trees it is surprising to notice that
the crustaceans may be entirely absent from many trunks, while when
another is examined which seems to differ very slightly, if at all, in
condition or situation, they are found in swarms. There is no doubt
but that the habits of woodlice would well repay the attention of
naturalists, who are now recognizing that besides anatomy as such, and
the classification which a knowledge of structure permits, there is the
equally important consideration of the creatures as they live their own
life and affect that of others. It is not our object to give a detailed
account of the ecology of British woodlice, but rather to provide a
basis from which it may be approached. Nevertheless a few general
remarks may not come amiss. Many points in the life-history of woodlice
may no doubt be learned by keeping them in captivity and there is just
sufficient difficulty in doing this successfully to give an interest to
the matter.

Apart from a supply of proper food, we take it that the chief object to
be attained is the provision of the amount of moisture required by the
particular species under examination, together with a sufficient supply
of air.

A great many interesting observations can be thus carried out, such
as those of Mr. Casserley, to which allusion has already been made.
The process of moulting for instance is well worth watching, and
although specimens with half their coat changed may be found in remote
corners, yet the whole course of the moult can be seen much better
in the case of captive woodlice. The following account is taken from
Mr. Casserley's description (75) of what happens in the case of
_Armadillidium vulgare_:--The approach of the moult is indicated by
the appearance of a white border on each segment of the body, which
becomes gradually more marked, while at the same time the animal is
seen to be less active and often makes a small burrow in which to
hide. Sometimes a sheltered corner against a stone is looked upon as
affording sufficient protection, but in either case each woodlouse
keeps to the place originally chosen. About ten days after the white
lines have become visible the animal appears to be divided into two.
Its skin is becoming loose and little movement can take place at the
joints of its body with the exception of that between the fourth and
fifth thoracic segments where the skin will ultimately break. The
woodlouse spends a day or two in this condition and then, by suddenly
walking forward, frees itself from the covering of the hinder portion
of its body. The three last pairs of walking legs are carefully pulled
out from the old skin, which now appears perfectly white, and at the
same time the lining of the hind portion of the alimentary canal (hind
gut) is also shed. After putting the tender half of his body well into
his corner or burrow the woodlouse proceeds to eat the part of his skin
that he has cast. The creature has now a very odd appearance. His front
half with the exception of the white edges is as it was before, the
rest of him instead of a light slaty blue, and is very soft as well as
proportionately a little larger.

In three days or so the tail end becomes hard and attains the normal
colour. Then the old skin from the front half is pushed off and the
creature becomes practically defenceless, so much so in fact, that any
of his species that happen to find him will attack him and eat all his
front half, rejecting, however, his now hardened tail-end.

Provided that the moulting woodlouse has survived (and in captivity, to
ensure this, he must be isolated), after three days his jaws will be
sufficiently hardened to allow of his eating, and usually he first of
all devours the second half of his cast skin. The operation of moulting
does not occupy quite so long a time in the case of young examples.
Specimens half-an-inch long do not moult more than once in six months
and show but little increase in size after the process.

Woodlice do not appear to live on either animal or vegetable food
alone, but adopt a mixed diet. It is, however, owing to their attacks
upon cultivated plants that the creatures are looked upon as pests by
the horticulturalist. The animals feed either in the night or in the
very early morning, on seedlings, orchid tubers, mushrooms, or anything
that comes to hand. Few of the accounts, however, of their ravages,
mention that the crustaceans have been caught absolutely in the act
of doing the damage ascribed to them. Some careful inquiries have
nevertheless enabled us to discover several observers who have watched
woodlice feeding. Mr. F. V. Theobald, of Wye College, and one of the
students at Swanley Horticultural College are among the number. The
former has also given us an account of the methods, out of many tried,
which he has found most successful for getting rid of the crustaceans.
Out of doors trapping with moss, sacking or horse-dung is best. In
glass houses, fumigation with hydro-cyanic acid gas has cleared them
out, and poison baits, especially potatoes cut and soaked in white
arsenic, have done some good. Stable manure is especially favourable to
these creatures, particularly when it is used "long": in this condition
it should therefore be avoided.

It is interesting to note how the woodlice in winter simply remain
where they happen to be so long as there is sufficient moisture, though
they are ready to run about as rapidly, for a time, as in summer,
should they happen to be disturbed.

No doubt many points of inter-relation between woodlice and other
animals remain to be discovered. Mr. John W. Odell tells us that on
Exmoor, in the open, he found no _Armadillidia_, though other forms
occurred under nine out of every ten stones that he turned over, and
here the smaller species of ants also abounded. Close to stone walls
_Armadillidia_ were to be seen to the exclusion of all other genera,
and this state of affairs was ascribed by Mr. Odell to the presence of
swarms of the large wood-ants which he considers would make short work
of any woodlice that could not protect themselves by rolling up.

We ought not to conclude this account without mentioning the fact that
woodlice once played an important part in medicine.

Doctor Fernie (28) gives some interesting extracts with regard to the
hog-louse and the woodlouse. The latter he seems to have identified
quite correctly as _Oniscus asellus_. He calls the former, however,
indiscriminately, "the common armadillo" (which is the old name for
the pill-woodlice now known as _Armadillidium_), "the pill millipede"
and "_Glomeris marginata_." The last two names are those of another
creature, not a crustacean, which when it is rolled up can be very
easily mistaken for an _Armadillidium_, though, when it uncurls, it
will be seen to have many more than seven pairs of legs. The local
appellations applied to the hog-louse by Doctor Fernie, and his remarks
with regard to its commonness, tend to show that it is _Armadillidium
vulgare_, to which he really refers, and the use of which in medicine
was commonly general.

Hog-lice were prescribed for scrofulous diseases and obstructions of
the liver and digestive organs, among other things, and the London
College of Physicians directed that the creatures should be prepared
by suspending them in a thin canvas bag placed within a covered vessel
over the steam of hot spirit or wine, so that being killed by the
spirit they might become friable. Hog-lice and Woodlice were also
administered alive, while the former were also put down the throats of
cows "to promote the restoration" of their cud, hence their name of
"cud-worm." There seems to be considerable evidence that even in modern
times Woodlice have had considerable remedial effect which depends upon
"an alkalescent fluid" contained in them.

=Local Names.=--Among the local names by which these creatures are
known are those of "sow bug," "lucre pig" (Berkshire), "carpenter"
and "chiselhog" (Berkshire). Doctor Fernie (28) gives a number of
others:--"thrush-louse," "tiggyhog," "cheslip," "kitchenball,"
"chiselbob," "lugdor," "palmer," and "cudworm." In the eastern
counties the same writer notes that they are known as "old-sows" or
"St. Anthony's hogs" while the Welsh call them "little grey-hogs," "the
little old women of the wood" or "grammar-sows," grammar signifying
a shrivelled up old dame. _Oniscus asellus_ was sometimes called
"socchetre," "church louse," and "chinch."

=Methods of Collection and Preservation.=--Woodlice should be collected
straightway into tubes or bottles half filled with 30 per cent.
methylated spirit.[3] Woodlice dropped into this weak spirit become
gradually narcotised and die, and they remain limp enough for purposes
of examination or to allow, of their legs and antennæ being set out
during the process of mounting. Specimens to be kept permanently should
be placed in 70 per cent. alcohol. For storage purposes the specimens
of each species from a given locality should be put together into a
small flat bottomed tube such as is used for pillules by apothecaries
or specially made for natural history purposes. A paper label on
which the name, locality, date of capture and any other necessary
particulars have been written with dark lead pencil, is not affected by
the spirit. The tubes may be corked, though if not frequently examined
all the spirit may evaporate, and cause the specimens to be spoilt. A
safer method is to plug the tubes with cotton wool and keep all those
containing a given species or specimens from a particular locality
beneath the surface of spirit in a large wide-mouthed bottle, into
which first of all some cotton wool has been put to prevent the tubes
from coming into sudden contact with the glass at the bottom. For show
purposes in museums, specimens taken direct from 30 per cent. spirit
should be mounted on slips of opal glass by means of gum-tragacanth
which has been powdered and shaken up in spirit before having water
added to it. The slips can be exhibited in glass tubes, six inches high
by one across, or in narrow stoppered museum jars. A variation of the
method is to mount the animals on clear glass and to place behind them
another strip of any colour that may be preferred.

=Classification.=--The various genera of woodlice are connected
together so closely, by intermediate forms, that their division into
families is, to a very great extent, arbitrary. Bate and Westwood
described but a single family Oniscidæ (I), though they distinguished
two sub-families:--Ligiinæ, which included the forms with many joints
to the flagellum of the antenna, and Oniscinæ, which contained the rest.

Since then the pill-woodlice have been thought by some to be
sufficiently different from the other genera to warrant their
separation, and three families namely, Ligiidæ, Oniscidæ, and
Armadillidæ have been recognized, as for instance by Dr. Scharff (63).

A fourth family--Trichoniscidæ--has been added by Professor G. O. Sars,
who in his _Crustacea of Norway_ (59) alludes to the division of the
tribe into the sections Ligiæ and Onisci and has adopted the following
classification:--

_Order_--=ISOPODA.=

_Tribe_--ONISCOIDA.

  _Family I._--LIGIIDAE.
             _Ligia._
             _Ligidium._

  _Family II._--TRICHONISCIDÆ.
              _Trichoniscus._
              _Trichoniscoides._
              _Haplophthalmus._

  _Family III._--ONISCIDÆ.
               _Oniscus._
               _Philoscia._
               _Platyarthrus._
               _Porcellio._
               _Metoponorthus._
               _Cylisticus._

  _Family IV._--ARMADILLIDIIÆ.
              _Armadillidium._

All the genera described by Professor Sars are represented in the
British Islands.

       *       *       *       *       *

Below is a scheme of classification and synopsis of the characters of
British genera of woodlice which we have compiled in order to render
easy the determination of the genus to which any particular specimen
may belong.

_SCHEME OF CLASSIFICATION AND SYNOPSIS OF GENERIC CHARACTERS._

_Order_--=ISOPODA.=

_Tribe_--ONISCOIDA.


_Section I._--=LIGIÆ.=

  _The Two Divisions of the Tail Appendages alike in Shape._

  (A.)--Flagellum with 10 or more joints; tail
         appendages wholly visible; head without
         lateral lobes                               LIGIIDAE.
            (1.)--Abdomen broad; body large;
                   habitat, the sea-shore            _Ligia._
            (2.)--Abdomen narrow; habitat, wet
                   moss                              _Ligidium._

  (B.)--Flagellum with less than 10 joints; head
         with small lateral lobes, tail appendages
         partly covered                              TRICHONISCIDÆ.
            (3.)--Abdomen narrow; eyes compound;
                   flagellum usually with more
                   than 3 joints                     _Trichoniscus._
            (4.)--Abdomen narrow; eyes simple or
                   wanting; flagellum with 4 joints  _Trichoniscoides._
            (5.)--Abdomen broad (comparatively);
                   eyes simple; back with
                   longitudinal ridges; flagellum
                   with 3 joints                     _Haplophthalmus._


_Section II._--=ONISCI.=

  _The Outer Divisions of the Tail Appendages Broader than the Inner._

  (A.)--Tail appendages projecting when the animal
         is walking                                  ONISCIDÆ.
      (a.)--Unable to roll up into a complete ball.
            (6.)--Flagellum with 3 joints; abdomen
                   broad; head, with lateral lobes   _Oniscus._
            (7.)--Flagellum with 3 joints; abdomen
                   narrow; head without lateral
                   lobes                             _Philoscia._
            (8.)--Flagellum with 1 joint; eyes
                   wanting; abdomen broad; habitat,
                   ant's nests                       _Platyarthrus._
            (9.)--Flagellum with 2 joints; abdomen
                   broad; frontal lobe projecting    _Porcellio_.
           (10.)--Flagellum with 2 joints; abdomen
                   narrow                            _Metoponorthus._
      (b.)--Able to roll up into a complete ball.
           (11.)--Flagellum with 2 joints; antennae
                   folded together over the thorax
                   when the animal is rolled up
                   into a ball                       _Cylisticus._

  (B.)--Tail appendages not projecting when the
         animal walking                              ARMADILLIDIIDÆ.
           (12.)--Flagellum with 2 joints; antennae
                   hidden or carried at the sides
                   of the head when the animal is
                   rolled up into a ball             _Armadillidium._

=British Species.=--Naturalists in this country paid little attention
to the recognition or description of Woodlice, until the latter half of
the nineteenth century.

In 1857 Kinahan read a paper before the British Association (32) in
which he described fourteen species of woodlice from the British
Islands, and eleven years later when Bate and Westwood published
their book (1), the number had risen to seventeen. One of the species
(_Oniscus fossor_), however, was doubtful, and although Dr. Scharff
in 1894 (63) rejected it, his list contained also seventeen species,
for in the meantime the Rev. T. R. R. Stebbing had found _Ligidium
hypnorum_ in Surrey (70).

Since then the Rev. Canon Norman, Dr. Scharff, the Rev. T. R. R.
Stebbing, and one of the present writers, have added other species, as
will be seen from the following pages, in which all those found, up to
the present time in the British Islands are described and figured.

We shall now consider in detail the British genera and species of
woodlice and give their synonymy and distribution.

_Order_--=ISOPODA.=

_Tribe--ONISCOIDA._


_Section_--=LIGIÆ.=

THE TWO DIVISIONS OF THE TAIL APPENDAGES ALIKE IN SHAPE.

_Family_--LIGIIDÆ.

=Flagellum with ten or more joints; tail appendages wholly visible;
head without lateral lobes.=

_Genus_--=LIGIA= Fabricius, 1798 (27), p. 301.

_Abdomen broad; body large; habitat, the sea-shore._

The genus _Ligia_ agrees with _Ligidium_ alone, in that the flagellum
of the larger antennæ has more than ten joints. In both genera, there
are no lateral lobes to the head, and the tail appendages are wholly
visible from the upper surface of the body. The latter in _Ligia_ is,
however, very many times bigger than in _Ligidium_ and shows no abrupt
decrease in the width of its segments when the abdomen is reached.

=Ligia oceanica= Linné (The Quay-louse). PLATE I.

  1767  _Oniscus oceanicus_ Linné (43), p. 1061.
  1793  _Cymothoa oceanica_ Fabricius (26), p. 509.
  1815  _Ligia scopulorum_ Leach (38), p. 374.
  1868  _Ligia oceanica_ Bate and Westwood (1), p. 444.
  1898  _Ligia oceanica_ Sars (59), 156, pl. LXX.

There is but one British species of _Ligia_, and this, the largest
member of the whole tribe to be met with in these Islands, usually
attains a length of two centimetres, while adult males may be nearly
half as long again. It is the _Oniscus oceanicus_ of Linnæus and lives
on the sea shore, where it may be found at low tide beneath stones and
rubbish in the crevices of timber. _Ligia_ forms a connecting link
between the woodlice proper and the many Isopods which actually live in
the sea.

The colour of the animals is a greenish grey, and the compound eyes
are almost black, so that they are very conspicuous; there are from
eleven to fourteen joints to the flagellum of the outer antennae and
this feature, taken in conjunction with the large size and habitat, is
sufficient to identify the species in question.

On the coast of Essex the name "quay-lowders" is given to these
crustaceans, "lowder" being apparently an old plural of louse.

[Illustration: FIG. 35.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Ligia oceanica_.]

It is worthy of mention that Mr. Webb, when in charge of the Marine
Biological Station at Brightlingsea, examined a very large male
specimen of _Ligia oceanica_, in which the maxillæ were duplicated and
consisted of four pairs instead of two.

_BRITISH LOCALITIES:--_

  _England_: Brightlingsea; (W.M.W.): Maldon; (W.M.W. from R.M.):
     Southend; (J.A.M.): Whitstable; (W.M.W.): Herne Bay; Margate;
     Dover; Folkestone; (J.A.M.)

  _Scotland_: Shetland to Cornwall; (Norman, 49).

  _Ireland_: East Coast; West Glengariff; Castletown; Berehaven;
     Bundoran; (Scharff, 63).

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; (25): Spain; (12): Denmark; Prussia; Norway;
     Faroe Islands; Belgium; (59).

  _Africa_: Morocco; (16).

_Genus_--=LIGIDIUM= Brandt, 1833 (3), p. 173. Zia, Koch (34).

_Abdomen narrow; habitat, wet moss._

In _Ligidium_ there are numerous joints to the flagellum, lateral
lobes are absent from the head, and the tail appendages are completely
to be seen. All the segments of the abdomen are distinctly narrower
than those of the thorax and in this it agrees with _Trichoniscus_,
_Trichoniscoides_, _Philoscia_, and _Metoponorthus_. In these, however,
the flagellum has never more than seven joints, the tail appendages (as
in all genera but _Ligia_ and _Ligidium_) are partially hidden by the
last segment, and in all the four but _Philoscia_ there are lobes to
the head.

=Ligidium hypnorum=, Cuvier. PLATE II.

  1792 _Oniscus hypnorum_ Cuvier (9), pl. XXVI., figs. 3-5.
  1793 _Oniscus agilis_ Persoon, quoted by Koch in Panzer (51),
        part 5, pl. XXIV.
  1830 _Ligia hypnorum_ Bosc (2), p. 179.
  1833 _Ligidium persoonii_ J. F. Brandt (3), p. 174, pl. IV.,
        figs. 6-7.
  1840 _Zia agilis_ Koch (34), part 34, pls. XXII. and XXIII.
  1844 _Ligidium personii_ Zaddach (77), p. 17.
  1853 _Ligidium personii_ Lereboullet (39), p. 14, pl. I., fig. 1,
        pl. II., figs. 20-31.
  1857 _Ligidium personii_ Kinahan (32), p. 275, pl. XXI., fig. 14,
        pl. XXII., fig. 9.
  1873 _Zia saundersii_ Stebbing (70), p. 286.
  1873 _Ligidium agile_ Norman (48), p. 419.
  1885 _Ligidium hypnorum_ Budde-Lund (8), p. 254.
  1898 _Ligidium hypnorum_ G. O. Sars (59), p. 158, pl. LXXI.

This species, which like the last, is the only British representative
of its genus, was added to our fauna in 1873 by the Rev. Thomas R. R.
Stebbing (70) who found specimens in the neighbourhood of Copthorne
Common, Surrey. Up to the present time, when we are pleased to announce
that we discovered it in the spring of 1902 at Warley in Essex,
_Ligidium hypnorum_ has not been recorded from any other place in the
British Islands.

[Illustration: FIG. 36.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Ligidium hypnorum_.]

As the name of the species implies, it lives in wet situations and in
its turn connects _Ligia_ with the forms which inhabit drier places.
_Ligidium hypnorum_ might be mistaken for _Philoscia muscorum_, but as
already pointed out in the generic description, the latter has but a
few (three) joints to the flagellum, instead of from ten to thirteen.
From _Ligia_, the species under consideration is distinguished by its
small size, narrow abdomen, and habitat.

_BRITISH LOCALITIES:--_

  _England_: Warley, Essex; (W.M.W.): Copthorne Common, Surrey;
     (Stebbing, 70).

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; (25): Sweden; Denmark; Germany; (59): Turkey; (8).

_Family_--TRICHONISCIDÆ.

=Flagellum with less than ten joints; head with lateral lobes; tail
appendages partly hidden.=

_Genus_--=TRICHONISCUS= Brandt, 1833 (3), p. 174.

_Abdomen narrow; eyes compound; flagellum, usually with more than three
joints._

In _Trichoniscus_ the flagellum may have from seven to four (rarely
three) joints. As in _Trichoniscoides_ and _Haplophthalmus_ there are
lateral lobes to the head, though these are not very pronounced; the
body is also of small size, the abdomen narrow with both divisions of
the tail appendages equally so, and almost of the same length though
slightly covered by the last segment. The compound eyes distinguish
_Trichoniscus_ from the two genera named, and from _Platyarthrus_,
while its small size and the character of its tail-parts mark it out
from all others.

=Trichoniscus pusillus= Brandt. Plate III.

  1833 _Trichoniscus pusillus_ Brandt (3), p. 174, pl. IV., fig. 9.
  1838 _Itea riparia_ Koch (34), part 22, pl. XVII.
  1844 _Itea lævis_ Zaddach (77), p. 16.
  1857 _Philougria celer_ Kinahan (32), p. 281, pl. XXII., figs. 1-4.
  1858 _Philougria riparia_ Kinahan (33), pp. 191 and 198, pl. XXIII.,
        fig. 1.
  1868 _Philougria riparia_ Bate and Westwood (1), p. 456.
  1898 _Trichoniscus pusillus_ Sars (59), p. 161, pl. LXXII., fig. 1.

This tiny species is found commonly amongst the roots of the herbage in
very moist places. It presents a horny translucent appearance and is
of a reddish brown colour. It runs with considerable speed, and when
it is moving, the white irregular lines with which it is beset are
not evident. _Trichoniscus pusillus_ is very much like _Trichoniscus
vividus_ in colour but the latter species is nearly twice as big and
has from five to seven joints to the flagellum, while the former has
never more than four. _Trichoniscus roseus_ is also much larger and
its bright red colour (which it loses, however, when preserved in
alcohol) is another means of distinguishing it from the species under
consideration.

Professor Sars in his _Crustacea of Norway_ (p. 162) describes from
Christiania, under the name of _Trichoniscus pygmæus_, a still smaller
species. As this may possibly be discovered in this country a brief
comparison between it and _Trichoniscus pusillus_ may be of value.
The former reaches a length of but two millimetres; it is "whitish,
semi-pellucid with a few light brown pigmentary ramifications across
the segments and a double row of irregular opaque patches along the
middle of its back" (p. 163). Its body is covered with minute tubercles
and there are only three joints to the flagellum; its movements are by
no means rapid.

[Illustration: FIG. 37.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Trichoniscus pusillus_.]

The body of _Trichoniscus pusillus_ is smooth and polished. It has four
joints to the flagellum--Dr. Scharff (63) says three or four--and it
moves quickly.

_BRITISH LOCALITIES:--_

  _England_: Brightlingsea; Warley; (W.M.W.): Epping Forest; (Bate
     and Westwood, 1): Hanwell; Southall; Kew Gardens; Langley; Burnham
     Beeches; Dropmore; Skirmett; Bluebell Hill, Maidstone; (W.M.W.):
     Chislehurst; Plymouth; Polperro; Looe; (Bate and Westwood, 1):
     Hertfordshire; Northumberland; Durham; (Norman, 49): Exeter;
     (Parfitt, 53).

  _Scotland_: Edinburgh; (Scott, 68): Cumbrae; (Robertson, 57).

  _Ireland_: Connemara; (Norman, 49): Dublin; Wexford; Cork and
     Kerry; (Percival Wright _teste_ Bate and Westwood, 1): Tyrone;
     Waterford; Portlaw; Kilkenny; Wicklow; (Kinahan, 33).

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; (25): Spain; (15): Italy; (19): Norway; Sweden;
     Denmark; Germany; (59).

  _Africa_: Algeria; Tunis; Azores; (24).

  _America_: Niagara; North America; (59).

=Trichoniscus vividus=, Koch. PLATE IV. (from a spirit specimen).

  1840  _Itea vivida_ Koch (34), part 34, pl. IV.
  1858  _Philougria vivida_ Kinahan (33), pp. 197 and 198, pl. XXIII.,
         fig. 2.
  1868  _Philougria vivida_ Bate and Westwood (1), Vol. II., pp. 458
         and 459, figs.

This species is claret-brown in colour and under a lens it is seen
to be marbled with white, indeed in appearance it is much like
_Trichoniscus pusillus_ though twice the size. There are important
differences between the two species as regards the number of joints to
the flagellum. These vary from five to seven in _Trichoniscus vividus_
while in the other, as already pointed out, there are not more than
four. The body is practically speaking smooth for it bears only very
small tubercles, widely separated. In _Trichoniscus vividus_ the
antennæ lack the bristles which characterise those of the other species
in the genus. The species under consideration was discovered by Dr.
Kinahan in March, 1858, at Portlaw, Co. Waterford and is active even
amongst the snow.

[Illustration: FIG. 38.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Trichoniscus vividus_.]

_BRITISH LOCALITIES:--_

  _Ireland_: Portlaw, Co. Waterford; (Kinahan, 33): Cappagh, Co.
     Waterford; (Scharff, Irish Nat., Vol. IX., p. 158): Borris, Co.
     Carlow; (Scharff, 64.)

_FOREIGN DISTRIBUTION:--_

  _Europe_: Spain; (12).

=Trichoniscus roseus= Koch. PLATE V.

  1838  _Itea rosea_ Koch (34), part 122, pl. XVI.
  1858  _Philougria rosea_ Kinahan (33), pp. 197 and 199, pl. XXIII.,
         fig. 3.
  1858  _Philougria rosea_ Bate and Westwood (1), p. 460.
  1898  _Trichoniscus roseus_ Sars (59), p. 163, pl. LXXIII., fig. 1.

The third British species of _Trichoniscus_ is of a deep pink colour
and has a light yellow stripe down the back (in some habitats the
animals are said to be quite white). Arranged in transverse rows upon
the body are large tubercles, each of which under strong magnification
will be found to end in a tiny hair. It is distinguished from
_Trichoniscus pusillus_ by the larger size of its body, which is
also comparatively broader, and from _Trichoniscus vividus_ by the
four joints of the flagellum of its antennæ which latter have strong
bristles upon them. In the former species there are five or more joints
to the flagellum and the antennæ, though hairy, lack the bristles.
_Trichoniscus roseus_ is to be looked for in old gardens.

[Illustration: FIG. 39.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Trichoniscus roseus_.]

_BRITISH LOCALITIES:--_

  _England_: Warley; (W.M.W.): Maldon; (W.M.W. from R.M.): Stanmore;
     Hanwell; Ealing; Wimbledon; (W.M.W.): Berkhamsted; Torquay;
     (Norman, 49): Plymouth; (Bate and Westwood, 1 and B.M.,):
     Grassendale, near Liverpool; (R.W.): Newtownards; (R.W., Irish
     Nat, 1904, p. 260.)

  _Scotland_: Tarbert; (Scot, 68).

  _Ireland_: Dublin; Ballyfinder, Co. Down; (Scharff, 63):
     Templeogue; Dundrum; Blackrock; Rathgar, Co. Dublin; Bray, Co.
     Wicklow; (R.F.S.): Oakleigh; Kerry; (R.W.): Belfast; (Welch, Irish
     Nat., 1896, p. 213.): At the grave of Josiah Welch (grandson of
     John Knox), Castle Upton; Richhill, Co. Armagh; Castleconnell
     Ferry; (R.W.): Glenade House, Co. Antrim; (R.W. from R. Ll.
     Praeger).

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; (25): Spain; (12): Italy; (59): Denmark;
     Germany; Holland; (39): Dalmatia; (18).

  _Africa_: Algeria; Tunis; (24).

_Genus_--=TRICHONISCOIDES=, Sars, 1898 (59), p. 164.

_Abdomen narrow; eyes simple; (or wanting); flagellum, with four
joints._

The members of this genus are very much like those of _Trichoniscus_.
In the latter, however, the hinder legs are longer in proportion and
the eyes are compound.

=Trichoniscoides albidus= Budde-Lund. PLATE VI.

  1879  _Trichoniscus albidus_ Budde-Lund (7) p. 9.
  1898  _Trichoniscoides albidus_ Sars (59), p. 165, pl. LXXIII.,
         fig. 2.

[Illustration: FIG. 40.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Trichoniscoides albidus_.]

We are able to include this species, as a specimen was found by Mr.
Webb at Eton Wick in the summer of 1899. It is one of a number of
species which the Rev. Canon Norman (49, p. 18) suggested as likely to
be British. It is the only representative of its genus, which does not
differ in any very important characters from the others in the family.
The narrow elongated body will serve to separate it from _Trichoniscus
vividus_ and _Trichoniscus roseus_, but on account of its size, which
is much the same as that of _Trichoniscus pusillus_ and the two British
species of _Haplophthalmus_, it will be advisable to give some further
points of distinction. From the first its white colour will serve
to differentiate it; the other two lack the narrow abdomen seen in
_Trichoniscoides albidus_. Moreover, not one of the three shows the
serrations on the side plates which characterise the species under
consideration. _Platyarthrus hoffmannseggii_ is small and white and
the edges of its side plates are toothed, but it is oval in shape,
possesses no eyes, and its stout antennæ have but a single joint to the
flagellum instead of four. On the Continent this species has been found
in rich soil.

_BRITISH LOCALITIES:--_

  _England_: Eton; (Stebbing, 71a): Sunderland; (Brady, 50a).


_FOREIGN DISTRIBUTION:--_

  _Europe_: France; Wimereux and Lyons, Forêt (25): Norway;
     Denmark; (59).

_Genus_--=HAPLOPHTHALMUS= Schöbl, 1850 (66), p. 449.

_Abdomen broad (comparatively); eyes simple; flagellum with three
joints; back with longitudinal ridges._

The body of _Haplophthalmus_ is long in proportion to its width, but
there is no abrupt decrease in the breadth of the abdomen as seen in
_Trichoniscus_ and _Trichoniscoides_. The eyes are simple as in the
latter genus and the lateral lobes of the head are rather large, while
the side plates of the body are well separated.

=Haplophthalmus mengii= Zaddach. PLATE VII.

  1844  _Itea mengii_ Zaddach (77), p. 16.
  1860  _Haplophthalmus elegans_ Schöbl (66), p. 449.
  1885  _Haplophthalmus mengii_ Budde-Lund (8), p. 250.
  1898  _Haplophthalmus mengii_ Sars (59), p. 167, pl. LXXIV.,
         fig. 1.

The Rev. Canon Norman discovered two specimens of this species in
Ireland in June, 1900 (50); in the previous year one of us (Mr. Webb)
found a single example at Eton Wick.

The main differences between the members of this genus and their allies
are set forth in the generic description and incidentally elsewhere, so
we shall content ourselves with giving the distinctive points of the
two British species. _Haplophthalmus mengii_ has a number of raised
longitudinal ribs on each segment of the thorax, the outer ridges being
somewhat broken. There are also two prominent ribs upon the third
segment of the abdomen.

[Illustration: FIG. 41.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Haplophthalmus mengii_.]

_BRITISH LOCALITIES:--_

  _England_: Eton; (Stebbing, 71a): Sunderland; (Brady, 50a).

  _Ireland_: Corcumroe Abbey; Co. Clare (Norman, 50).

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; (25): Norway; Prussia; Germany; Bohemia; (59).

=Haplophthalmus danicus= Budde-Lund. PLATE VIII.

  1870  _Haplophthalmus elegans_ Budde-Lund (6), p. 228
         (not _Haplophthalmus elegans_ Schöbl).
  1879  _Haplophthalmus danicus_ Budde-Lund (7), p. 9.
  1881  _Haplophthalmus mengii_ Weber (76), p. 192, pl. V., figs. 7-9
         (not _Itea mengii_ Zaddach).
  1885  _Haplophthalmus danicus_ Budde-Lund (8), p. 250.
  1898  _Haplophthalmus danicus_ Sars (59), p. 168, pl. LXXIV., fig. 2.

This species was added to the British list by the Rev. Canon Norman
(49), who found a colony in his garden at Berkhamsted. It has rows of
tubercles on its thorax instead of ridges, and there are no ribs at all
upon the abdomen. The front of the head projects further comparatively
and forms a more acute point than in _Haplophthalmus mengii_ and it is
not so purely white in colour as the latter species.

[Illustration: FIG. 42.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Haplophthalmus danicus_.]

_BRITISH LOCALITIES:--_

  _England_: Warley Place; (W.M.W. from Miss Willmott): Queen's
     Cottage, Kew Gardens; Stanmore; Hanwell, garden at Odstock,
     Bennett's Nurseries; (W.M.W.): Berkhamsted; (Norman, 49):
     Sunderland; (Brady, 50a).

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; (25): Denmark; Holland; Germany; (Dollfus, Feu
     de Jeun, Nat., April, 1896): Norway; (Sars, 59).


_Section_--=ONISCI.=

THE OUTER DIVISIONS OF THE TAIL APPENDAGES BROADER THAN THE INNER ONES.

_Family_-ONISCIDÆ.

=Tail appendages projecting when the animal is walking.=

  (1.) Unable to roll up into a complete ball.

_Genus_-=ONISCUS= Linné 1746 (41), p. 360.

_Flagellum, with three joints; abdomen broad; head with lateral lobes._

The characters given above taken in conjunction with the size of the
animals will serve to distinguish the members of this genus.

=Oniscus asellus= Linné (The "Common Slater.") PLATE IX.

  1761  _Oniscus asellus_ Linné (41), p. 500, No. 2058.
  1792  _Oniscus murarius_ Cuvier (9), p. 22, pl. XXVI.
  1838  _Oniscus fossor_ Koch (34), part 22, pl. XXII.
  1868  _Oniscus asellus_ Bate and Westwood (1), p. 468.
  1868  _Oniscus fossor_ Bate and Westwood (1), pp. 471-2.
  1898  _Oniscus asellus_ Sars (59), p. 171, pl. LXXV.

_Oniscus asellus_ is one of the largest of our woodlice and it is also
probably the commonest, though _Porcellio scaber_ is in many places
quite as abundant. The body of _Oniscus_ is broad and expanded and the
colour is usually a slate grey with yellowish markings more or less
regularly arranged.

From the genus _Porcellio_ the species with which we are concerned
is at once distinguished by the three jointed flagellum. _Porcellio_
has but two joints and has, besides, a prominent lobe projecting from
the middle of the head, which is not seen in _Oniscus_. _Philoscia_,
although it has three joints to the flagellum, has a narrow abdomen
and lacks entirely the lateral lobes which are a feature of the other
genera of Oniscidæ.

_Oniscus fossor_ of Koch (34) was recognized by Kinahan and by Bate and
Westwood as a species. Dr. Scharff submitted specimens to Professor
Budde-Lund who found no differences between them and _Oniscus asellus_.
The former (63) mentions, however, that the characteristics of the
supposed species are those of young examples of _Oniscus asellus_, and
Professor Sars (59, p. 173) seems to be of the same opinion. Many young
examples of _Oniscus asellus_ that we have examined have a curious
whitish transverse band owing to the light colour of the dorsal plates
of the first abdominal segments. The flagellum also does not seem to
shew in young animals a distinct division into three joints.

[Illustration: FIG. 43.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Oniscus asellus_.]

_BRITISH LOCALITIES:--_

  _England_: High Beach, Epping, including an albino; Maldon;
     Brightlingsea; Iver; Hanwell; Eton; Kew; Pamber Forest;
     Kingston-on-Soar; Bluebell Hill, Maidstone; (W.M.W.):
     Lynmouth; (W.M.W. from J.T.C.).

  _Scotland_: (Scharff, 63). Dinnet, Aberdeenshire; (W.M.W. from
     Madame Christen).

  _Ireland_: (Scharff, 63). Yellow form with black spots, Donegal (R.W.)

_FOREIGN DISTRIBUTION:--_

  _Europe_: Almost throughout; (12): France; (25): Spain; (12):
     Sweden Norway; Denmark; Germany; Holland; Italy; Iceland; (59):
     Faroe Islands; Thorsharn; (R.F.S.)

  _Africa_: Azores; (24).

  _America_: Greenland; (59): North America; (Budde-Lund).

_Genus_--=PHILOSCIA= Latreille, 1804 (37), p. 43.

_Flagellum with three joints; abdomen narrow; head without lateral
lobes._

If any further differences of an obvious kind be required to
distinguish _Philoscia_ from _Oniscus_, one at least will be found in
the much greater development of the hinder legs in the former genus.

=Philoscia muscorum= Scopoli. PLATE X.

[Not of Lereboullet, which is an _Oniscus_, see Bate and Westwood (1).]

  1763  _Oniscus muscorum_ Scopoli (67), p. 415.
  1793  _Oniscus sylvestris_ Fabricius (26), p. 397.
  1793  _Oniscus agilis_ Koch in Panzer (51), part 9, pl. XXIV.
  1833  _Philoscia marmorata_ Brandt (3), p. 183.
  1838  _Ligia melanocephala_ Koch (34), part 22, pl. XVIII.
  1847  _Zia melanocephala_ Koch (38), part 40, pl. I. p. 212.
  1868  _Philoscia muscorum_ Bate and Westwood (1), p. 450.
  1898  _Philoscia muscorum_ Sars (59), p. 174, pl. LXXVI., fig. 1.

This species lives chiefly at the roots of grass and under the stones
or sticks that lie among it. _Philoscia muscorum_ has a very smooth and
shining body, and its long legs enable it to move very rapidly. The
ground colour of its dorsal surface varies from light yellow to deep
brown. There are characteristic dark markings down the middle of the
thorax and on the sides, between which are lighter patches. In dark
coloured specimens the markings are by no means so evident.

[Illustration: FIG. 44.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Philoscia muscorum_.]

_BRITISH LOCALITIES:--_

  _England_: High Beach, Epping; Warley; (W.M.W.): Maldon; (W.M.W.
     from R.M.): Kew; Langley; Hanwell, yellow variation; Bluebell
     Hill, Maidstone; (W.M.W.): Liphook; (C.S.): Pamber Forest;
     Kingston-on-Soar; (W.M.W.)

  _Scotland_: (Scott, 68).

  _Ireland_: Almost throughout; (Scharff, 63).

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; (25): Spain; (12): Sicily; (19): Hertsogovinia;
     (22): Sweden; (21): Norway; Denmark; Prussia; Germany; Holland;
     Poland; Austria; Italy; (59): Sardinia; (21).

  _Africa_: Algeria; Tunis; (24).

=Philoscia couchii= Kinahan. PLATE XI.

  1858  _Philoscia couchii_ Kinahan (33), p. 195, pl. XXIII., fig. 4.
  1868  _Philoscia couchii_ Bate and Westwood (1), p.
  1885  _Ligidium couchii_ Budde-Lund (8), p. 257.
  1885  _Philoscia longicornis_ Budde-Lund (8), p. 221.
  1897  _Philoscia couchii_ Dollfus (21), p. 72, pl. I., fig. 1.

_Philoscia couchii_ is an inhabitant of the sea-side; it is smaller
than the last species, its colour to the naked eye is a uniform
lead-grey, and its antennæ are very large (compared with its size) and
hairy.

This species was discovered by Professor Kinahan when in the company of
Messrs. Bate and Westwood near Polperro in Cornwall in the year 1858,
and dried specimens presented by him are in the British Museum (Natural
History).

_BRITISH LOCALITIES:--_

  _England_: Talland Cove; Polperro; (Bate and Westwood, 1): Salcombe,
     Devon; (Norman, 49): Meadefoot, Torquay; (Stebbing in 49).

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; (25): Spain; (12): Sicily; (19): Sebastopol;
     (Norman, 49).

  _Africa_: Azores; Canaries; Morocco; Algiers; Tunis: Egypt
     Senegal; (24).

  _Atlantic Isles_: Canaries; Azores; (21).

  _Asia_: Syracuse; Bazone (18).

[Illustration: FIG. 45.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Philoscia couchii_.]

_Genus_--=PLATYARTHRUS= Brandt, 1833 (3), p. 174.

[_Typhloniscus_ Schöbl (66), p. 279.]

_Flagellum with one joint; eyes wanting; abdomen broad; habitat, ants'
nests._

The broad body, which is much flattened, and the very thick
antennæ distinguish _Platyarthrus_ from the other small woodlice
(Trichoniscidæ).

=Platyarthrus hoffmannseggii= Brandt. PLATE XII.

  1833  _Platyarthrus hoffmannseggii_ Brandt (3), p. 174, pl. IV.,
         fig. 10.
  1844  _Itea crassicornis_ Koch (34), part 36, pl. V.
  1860  _Typhloniscus steinii_ Schöbl (66), p. 282.
  1868  _Platyarthrus hoffmannseggii_ Bate and Westwood (1), p. 464.
  1898  _Platyarthrus hoffmannseggii_ Sars (59), p. 175, pl. LXXVI.,
         fig. 2.

Up to the present this is the only woodlouse which has been found in
the nests of British ants. It is small and oval, its colour is white,
and its body is covered with tubercles. The edges of its side plates
are toothed, its flagellum has but a single joint and it has no eyes.

Miss Kate Hall tells us that, if very hungry, ants in captivity will
kill and eat _Platyarthrus_. With regard to its own food, Lord Avebury
has favoured us with the opinion that it lives on the spores of the
lower plants, such as would be found in the ants' nest.

[Illustration: FIG. 46.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Platyarthrus hoffmannseggii_.]

_BRITISH LOCALITIES:--_

  _England_: Warley; Hanwell; West Drayton; Langley;
     Kingston-on-Soar; Bluebell Hill, Maidstone; (W.M.W.): Berkhamsted;
     Salcombe; Devon; Cheddar Cliffs, Somerset; (Norman, 49): Ide, near
     Exeter; (Parfitt, 53): Torquay; (Stebbing in 49); Lulworth Cove;
     (Rev. A. R. Hogan _teste_ Bate and Westwood, 1): Hammersmith;
     Oxford; Berry Head, Torquay; Plymouth; (Bate and Westwood, 1): In
     the nest of _Myrmica rubra_, Newton Ferrers (E. E. Lowe).

  _Scotland_: Banff; (Thomas Edward in 49).

  _Ireland_: Leixlip, Co. Dublin; Lismore, Co. Waterford; Glengariff,
     Co. Cork; (Scharff, 63): Bagenalstown, Co. Carlow; (64).

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; (28): Spain; (12): Denmark; Germany; Holland;
     Bohemia; Austria; Tyrol; Helvetia; (59).

       *       *       *       *       *

  NOTE.--In the genera which follow, air-tubes or air-cavities
     (tracheæ) are present in the outer plates of the abdominal
     appendages, 1 and 2, or 1 to 5. The appendages in question have
     in consequence a milk-white appearance in the living animal
     owing to the fact that the enclosed air reflects white light.
     Considerable interest attaches to the study of these tracheæ,
     which have the same function as those of insects, but which have
     been independently developed. To emphasise the latter fact the
     structures are often termed "pseudotracheæ."

_Genus_--=PORCELLIO= Latreille, 1804 (37), p. 45.

_Flagellum, with two joints; abdomen, broad; frontal lobe projecting._

_Porcellio_ is easily separated from the previous genera--_Oniscus_,
_Philoscia_, and _Platyarthrus_--by its two-jointed flagellum. The
fact that the abdomen is not abruptly narrowed separates it from
_Metoponorthus_, which also lacks the prominent frontal lobe so
characteristic of _Porcellio_. The species of this genera might be
confused with _Cyclisticus_ which has two joints to the flagellum and
a broad abdomen, but the latter genus has the power of rolling itself
into a ball, while its frontal lobe is very small, and the first
segment of its thorax is comparatively larger than in any species of
_Porcellio_.

=Porcellio scaber= Latreille. PLATE XIII.

  1804  _Porcellio scaber_ Latreille (37), p. 45.
  1818  _Oniscus granulatus_ Lamark (36), p. 261.
  1818  _Porcellio nigra_ Say (62), p. 432.
  1840  _Porcellio brandtii_ Milne-Edwards (46), p. 168.
  1840  _Porcellio dubius_ Koch (34), part 34, pl. VIII.
  1847  _Porcellio asper_ Koch (35), p. 207, pl. VIII., fig. 98.
  1857  _Porcellio montezumæ_ Saussure (60), p. 207.
  1865  _Porcellio paulensis_ Heller (31), p. 136, p. XII., fig. 5.
  1868  _Porcellio scaber_ Bate and Westwood (1), p. 475.
  1876  _Porcellio graniger_ Miers (44), p. 223.
  1885  _Porcellio graniger_ Budde-Lund (8), p. 149.
  1898  _Porcellio scaber_ Sars (59), p. 176, pl. LXXVII.

The body of _Porcellio scaber_ is densely covered with tubercles. Its
colour is usually of a very dark grey, but at times it is quite red or
variegated with yellow. Albino specimens have been recorded. The two
joints of the flagellum are of the same length and together equal that
of the last joint of the peduncle. Air-tubes are present in the outer
plates of the first two abdominal appendages.

[Illustration: FIG. 47.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Porcellio scaber_.]

_BRITISH LOCALITIES:--_

  _England_: High Beach, Epping; Warley; Brightlingsea; (W.M.W.):
     Maldon; (W.M.W. from R.M.): Langley; Kew; Skirmett; Pamber Forest;
     (W.M.W.): Liphook; (C.S.): Stoke-on-Trent; Kingston-on-Soar;
     (W.M.W.)

  _Scotland_: Dinnet (W.M.W. from Madame Christen).

  _Ireland_: Common everywhere; (Scharff, 63.)

_FOREIGN DISTRIBUTION:--_

  _Europe_: Throughout; (59): France; (28): Spain; (15): Iceland;
     (59): Faroe Isles--Thorsharn and Naalsoe--(R.F.S. and B.M., N.
     Annadale).

  _America_: Greenland; North America; Sandwich Isles; (B.M.);
     Mexico; (59): St. Paul; St. Croix; (59); Ascension; Tristan
     d'Acunha; (23)

  _Asia_: Ceylon; Kamtschatka: (23).

  _Australia_: Melbourne; Sydney; Tasmania; New Zealand; (B.M.,
     Chilton).

  _Africa_: Azores; Canaries; Cape of Good Hope; (24).

=Porcellio pictus= Brandt and Ratzeburg. PLATE XIV.

  1833  _Porcellio pictus_ Brandt and Razteburg (4), p. 78, pl. 12,
         fig. 5.
  1839  _Porcellio melanocephalus_ Koch (34), part 28, pl. XVIII.
  1853  _Porcellio melanocephalus_ Schnitzler (65), p. 24.
  1856  _Porcellio mixtus_ Fitch (29), p. 120.
  1868  _Porcellio pictus_ Bate and Westwood (1), p.
  1898  _Porcellio pictus_ Sars (59), p. 177. pl. LXXVII., fig. 1.

There are tubercles on the body of _Porcellio pictus_, which is a
striking looking animal. Its head is black with the lateral lobes
curved outwards; there is a dark band down the middle of the back and
commonly two others on each side, with more or less conspicuous yellow
markings between.

The distal (terminal) joint of the flagellum is but half the length of
the proximal one and the last peduncular joint is longer than the two
combined.

The abdominal appendages--1 and 2--are provided with air-tubes.

[Illustration: FIG. 48.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Porcellio pictus_.]

_BRITISH LOCALITIES:--_

  _England_: Maldon; (W.M.W. from R.M.): Chislehurst; (Bate and
     Westwood, 1): Cooper's Hill, near Cheltenham; (Norman, 49):
     Exeter; (Parfitt, 53): Kent; (Bate and Westwood, 1.)

  _Scotland_: Between Leith and Portobello; (Scott, 68): Cumbrae
     (Scott, 68a): Ayrshire; (Boyd in Norman, 49): Banff; (T. Edwards
     in Norman, 49).

  _Ireland_: Dublin; Belfast; (Bate and Westwood, 1): Galway;
     Maryborough; Queen's Co., Castel; and Caher Co. Tipperary; (R.F.S.)

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; (25): North, West-Central, and East Europe; (8):
     Sweden; Norway; Denmark; Germany; Hungary; Russia; (59).

  _North America_: (8).

=Porcellio dilatatus= Brandt. PLATE XV.

  1833  _Porcellio dilatatus_ Brandt and Ratzeburg (4), p. 78, pl. 12.,
         fig. 6.
  1840  _Porcellio scaber_ Milne-Edwards (not Latreille) (46), p. 167.
  1868  _Porcellio dilatatus_ Bate and Westwood (1), p.
  1898  _Porcellio dilatatus_ Sars (59), p. 179, pl. LXXVII., fig. 2.

The fact that _Porcellio dilatatus_ is more than half as broad as it is
long, at once distinguishes it from the other species of _Porcellio_.
It is tuberculated and of somewhat a lighter grey than _Porcellio
scaber_ usually is. The two species agree in having the two joints of
the flagellum equal, but the last peduncular joint, as in _Porcellio
pictus_, is longer than the flagellum.

As in the two preceding species, air-tubes are found in the outer
plates of the appendages on the first two abdominal segments.
_Porcellio dilatatus_ is to be looked for near houses.

[Illustration: FIG. 49.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Porcellio dilatatus_.]

_BRITISH LOCALITIES:--_

  _England_: Maldon; (W.M.W. from R.M.): Eton; (Stebbing from
     W.M.W., 71a): Berkhamsted; (Norman, 50): Headley, Surrey; Ventnor;
     (Stebbing in Norman, 49).

  _Ireland_: Dublin; (Scharff, 63): Dundrum; (Scharff in Norman,
     50): Galway; Roundstone; (R.F.S.): Belfast; (C. W. Buckle, Irish
     Nat., Vol. XI. (1902), p. 43).

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; (25): Spain; (12 ): Denmark; Norway; Germany;
     Poland; Holland; (59).

  _Africa_: Madeira; Azores; (24).

  _Australia_: New Guinea; (59).

=Porcellio rathkei= Brandt. PLATE XVI.

  1833  _Porcellio rathkei_ Brandt (3), p. 177, fig. 10.
  1833  _Porcellio ferrugineus_ Brandt (3), p. 178.
  1840  _Porcellio trilineatus_ Koch (34), part 34, pl. IX.
  1853  _Porcellio trivittatus_ Lereboullet (39), p. 54, pl. I.,
         figs. 13 and 14.
  1853  _Porcellio tetramoerus_ Schnitzler (65), p. 24.
  1853  _Porcellio striatus_ Schnitzler (65), p. 24.

There is often a light band down the back and one on either side of it
near the margin in _Porcellio rathkei_ (especially in the males), with
other more irregularly arranged light patches between. Unlike the three
species previously considered, the present one has a smooth body. The
distal joint of the flagellum is the longer, and the flagellum itself
is equal in length to the last joint of the peduncle.

Some specimens found by Mr. Webb in 1899 at Eton were submitted to Mr.
Stebbing, and since then the former has found _Porcellio rathkei_ to
be pretty generally distributed in West Middlesex, where the species
appears to frequent the open fields.

Air-tubes occur in abdominal appendages 1 to 5 and the white appearance
of all of these at once serves to distinguish the living animal from
_Porcellio scaber_ in which the first two pairs of abdominal appendages
alone are white.

_BRITISH LOCALITIES:--_

  _England_: Eton; (Stebbing, 71a): Lane End; (Stebbing, from the
     Misses Johnston, 71a): Acton; Ealing; Hanwell; Southall; Northolt;
     Greenford; West Drayton; Mortlake; (W.M.W.); Sunderland; (Brady,
     50a).

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; (25): Bosnia; Servia; (22): Hertzogovania
     (B.M.); Norway; Northern, Western, and Middle Europe, everywhere;
     (59): Corfu (B.M.)

  _Asia_: Transcaucasia; (59).

  _North America_: (59).

[Illustration: FIG. 50.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Porcellio rathkei_.]

=Porcellio laevis= Latreille. PLATE XVII.

  1804  _Porcellio laevis_ Latreille (37), p. 46.
  1827  _Porcellio degeerii_ Savigny and Audouin (61), p. 289.
  1833  _Porcellio cucercus_ Brandt (3), p. 177.
  1833  _Porcellio syriacus_ Brandt (3), p. 178.
  1833  _Porcellio musculus_ Brandt (3), p. 180.
  1833  _Porcellio cinerascens_ Brandt (3), p. 178.
  1833  _Porcellio dubius_ Brandt (3), p. 178.
  1837  _Porcellio poeyi_ Guérin (30), p. 6.
  1844  _Porcellio urbicus_ Koch (34), part 36, pl. IV.
  1847  _Porcellio flavipes_ Koch (35), p. 206, pl. VIII., fig. 97.
  1853  _Cylisticus laevis_ Schnitzler (65), p. 25.
  1857  _Porcellio cubensis_ Saussure (60), p. 307.
  1857  _Porcellio sumichtasli_ Saussure (60), p. 307.
  1857  _Porcellio cotillæ_ Saussure (60), p. 307.
  1857  _Porcellio aztecus_ Saussure (60), p. 307.
  1857  _Porcellio mexicanus_ Saussure (60), p. 307.

Another smooth species is _Porcellio laevis_. The colour of its body
is light grey with irregular white markings. The large size of this
species and the very long tail-appendages of the males are features
which will help to identify it. The distal joint of the flagellum is
slightly the longer and as in the last species (_P. rathkei_) the
flagellum is equal in length to the last joint of the peduncle. The
chief habitats for this species are among vegetable rubbish near human
dwellings.

Only the first two abdominal appendages contain air-tubes.

[Illustration: FIG. 51.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Porcellio laevis_.]

_BRITISH LOCALITIES:--_

  _England_: Maldon; (W.M.W. from R.M.): Ipswich (1892); Hanwell;
     Wimbledon; (W.M.W.): Kent; (Kinahan, 32).

  _Ireland_: Dublin; (Bate and Westwood, 1): Blackrock Dundrum; Co.
     Dublin; Galway; (R.F.S.)

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; (25): Spain; (15): Sicily; (19): Hertzogovania;
     (22): Sweden; Denmark; Germany; Belgium; Austria; Italy; Dalmatia;
     Greece; Turkey; (59); Corfu; (B.M.): Inca, Majorca (23);
     (B.M.--Pocock and Thomas.)

  _Asia_: Syria; Turkestan; (21).

  _Africa_: Morocco; Algeria; Tunis; Tripoli; Senegal; Egypt; (23).

  _Atlantic Isles_: Bermudas; Azores; Canaries; Cape Vera; Madeira;
     (24).

  _America_: North America; Mexico; Peru; Brazil; Chili; West
     Indies; Pacific Islands; (59); Sandwich Isles; (B.M.)

=Porcellio ratzeburgii= Brandt. PLATE XVIII.

  1833  _Porcellio ratzeburgii_ Brandt, (3), p. 178.
  1839  _Porcellio nemorensis_ Koch (34), part 28, pl. XIX.
  1839  _Porcellio lugubris_ Koch (34), part 28, pl. XX.
  1853  _Porcellio quercum_ Schnitzler (65), p. 24.
  1898  _Porcellio ratzeburgii_ Sars (59), p. 182, pl. LXXX, fig. 1.

There are granulations on the middle of the segments in _Porcellio
ratzeburgii_ and the sides of its body are more nearly parallel than
in the other species of _Porcellio_; the frontal lobe is, practically
speaking, semicircular and the lateral plates of the thorax flank the
head to a considerable extent. As in _Porcellio pictus_, the dark band
is in the middle of the back. The distal joint of the flagellum is
nearly twice as long as the proximal, and the flagellum is shorter than
the last joint of the peduncle. This species was added to the British
list by Mr. Webb (74) in 1898.

_Porcellio ratzeburgii_ agrees with _Porcellio rathkei_ in having
air-tubes in the first five abdominal appendages.

[Illustration: FIG. 52.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Porcellio ratzeburgii_.]

_BRITISH LOCALITIES:--_

  _England_: Warley; Brightlingsea; young examples (W.M.W.): Maldon;
     young examples (W.M.W. from R.M.)

_FOREIGN DISTRIBUTION:--_

  _Europe_: Trafoi St. Martini, and Capitello, in the Tyrol;
     (Norman, 50); East Alps, very common; Val-de-Joux; Massif de la
     Chartreuse Vaulnaveys (25): Bosnia; (22): Norway; Central Europe;
     Upper Pfaltz; Bohemia; Saxony; Rhaetia; (59).

_Genus_--=METOPONORTHUS= Budde-Lund, 1879 (7), p. 4. _Porcellionides_
Miers, 1876 (44), p. 98.

_Flagellum, with two joints; abdomen, narrow; frontal lobe not
developed._

The hinder legs of _Metoponorthus_ are proportionately longer than in
any other Oniscidæ save _Philoscia_. Both genera have a narrow abdomen,
but _Philoscia_ has an extra joint to the flagellum, and shows no sign
of lateral lobes to the head.

=Metoponorthus pruinosus= Brandt. PLATE XIX.

  1833  _Porcellio pruinosus_ Brandt (3), p. 181.
  1840  _Porcellio truncatus_ Milne-Edwards (46), p. 173.
  1840  _Porcellio maculicornis_ Koch (34), part 34, pl. XVI.
  1853  _Porcellio frontalis_ Lereboullet (39), p. 63, pl. I, fig. 17.
  1868  _Porcellio pruinosus_ Bate and Westwood (1), p. 487.
  1877  _Porcellio (Porcellioides) flavo-vittatus_ Miers (45), p. 669,
         pl., LXVIII., fig. 4.
  1898  _Metoponorthus pruinosus_ Sars (59), p. 184, pl. LXXX., fig. 2.

Undamaged specimens of _Metoponorthus pruinosus_ are of a beautiful
bluish-grey colour, owing to a "bloom" which is easily brushed off,
revealing a dark reddish-brown tint beneath it. The antennæ are long
and have white markings upon them.

Air-tubes occur in the first two abdominal appendages.

[Illustration: FIG. 53.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Metoponorthus pruinosus_.]

_BRITISH LOCALITIES:--_

  _England_: Maldon; (W.M.W. from R.M.): Hanwell; Eton Wick; Kew;
     Ipswich; Stoke-on-Trent; (W.M.W.): Chiselhurst; Oxford; (Bate and
     Westwood): Berkhamsted; Burnmoor; Durham; (Norman, 49): Exeter;
     (Parfitt, 53); Torquay; (B.M.--T.R.R.S.)

  _Scotland_: Banff; (Thomas Edwards in Norman, 49)

  _Ireland_: Dublin; (Kinahan, 32): Foyle District; Donegal; Galway;
     Clonbrock, Co. Galway; Mornington, Co. Meath; Santry; Gleeson
     Park; Dundrum, Co. Dublin; Bray; (R.F.S.)

_FOREIGN DISTRIBUTION:--_

  _Europe_: Practically all the Countries of Europe are given in
     Dollfus' list; (23).

  _Asia_: Japan; China; Syria; Ceylon; Sumatra; Celebes;
     Phillipines; Caucasus; Himalayas; (23): Christmas Island; (B.M.)

  _Africa_: Generally distributed; Madagascar; Seychelles; (23).

  _Atlantic Isles_; (23).

  _America_: North and South, almost everywhere, to judge from M.
     Dollfus' list; (23).

  _Australia_: New Caledonia; (23).

=Metoponorthus cingendus= Kinahan. PLATE XX.

  1857 _Porcellio cingendus_ Kinahan (32), p. 279, pl. XIX.,
        figs. 1468-9.
  1868 _Porcellio cingendus_ Bate and Westwood (1), p. 489.
  1885 _Metoponorthus simplex_ Budde-Lund (8), p. 188.

The colour of _Metoponorthus cingendus_ is steel blue with red or
yellowish spots. It has a raised line across each thoracic segment and
its abdomen is narrower than in _Metoponorthus pruinosus_.

[Illustration: FIG. 54.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Metoponorthus cingendus_.]

_BRITISH LOCALITIES:--_

  _England_: Salcombe, Devon; (Norman, 49): South Devon; (Stebbing
     in 49).

  _Ireland_: Dublin; (B.M. from Kinahan); Mountain Districts of
     Dublin, Wicklow, and Cork; Coast of Kerry; Arran Islands; Achill,
     Co. Mayo; Roundstone, Co. Galway; Mallow, Caef Island; Glandore;
     Brock Haven, Co. Cork; Killoughrim Forest, Co. Wexford; Kenmare,
     Co. Kerry; (R.F.S.).

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; (25): Spain; (12).

  (2.) Able to roll up into a ball.

_Genus_--=CYLISTICUS= Schnitzler, 1853 (65), p. 24.

_Flagellum, with two joints; abdomen broad; frontal lobe, very small._

The characters given immediately above are almost those of _Porcellio_
with which _Cylisticus_ might, perhaps, be confounded. The latter
has the power, however, of rolling itself into a ball, and the first
segment of the thorax is comparatively larger than in any species of
_Porcellio_, indeed the side plates of the segment in question entirely
flank the head. These features, as well as the straight sides of the
body and the arched back, connect _Cylisticus_ with _Armadillidium_,
from which the former is, however, at once separated by its long
pointed tail appendages.

=Cylisticus convexus= De Geer. PLATE XXI.

  1778  _Oniscus convexus_ De Geer (10), p. 553, pl. XXXV., fig. 11.
  1833  _Porcellio spinifrons_ Brandt (3), p. 177.
  1836  _Porcellio laevis_ Koch (34), part 6, pl. I.
  1853  _Porcellio armadilloides_ Lereboullet (39), p. 65. pl. I.,
         fig. 18.
  1853  _Cylisticus laevis_ Schnitzler (65), p. 25.
  1868  _Porcellio armadilloides_ Bate and Westwood (1), p. 485.
  1898  _Cylisticus convexus_ Sars (59), p. 186, pl. LXXXI.

There is but a single species of _Cylisticus_ found in this country,
so that it is not necessary for us to go into much further detail with
regard to it. _Cylisticus convexus_ has the two joints of the flagellum
about equal, and they together in turn closely approximate in length to
the last joint of the peduncle. Mr. Stebbing says, in a letter, that
British examples do not appear to have the "white tail-piece" seen in
Continental ones. It is not noticeable in the preserved specimens which
we have seen from Berkhamsted and Leixlip, but it is very evident in
the living ones found at Hanwell and Maidstone.

The abdominal appendages 1 to 5 are provided with air-tubes.

[Illustration: FIG. 55.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Cylisticus convexus_.]

_BRITISH LOCALITIES:--_

  _England_: Maldon; (W.M.W. from R.M.): Hanwell; Bluebell Hill,
     Maidstone; Eton; (W.M.W.): Berkhamsted; Portland; (Norman, 49).

  _Scotland_: Salisbury Crags; Edinburgh; Lanarkshire; Rothesay;
     (Scott, 68): Killwinning; (John Smith _fide_ Robertson, 57):
     Highgate; (Bate and Westwood, 1).

  _Ireland_: Leixlip, Co. Dublin; Tempo, Co. Fermanagh; Goresbridge,
     Co. Kilkenny; (R.F.S.)

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; (25): Sweden; Norway; Denmark; Germany; Bohemia;
     Holland; Belgium; Turkey; Caucasus; (59).

  _North America_; (59).

_Family_--ARMADILLIDIIDÆ.

=Tail appendages not projecting when the animal is walking.=

_Genus_--=ARMADILLIDIUM= Brandt, 1833 (3), p. 184.

_Flagellum, with two joints; outer division of the tail appendages
expanded and broader at the hinder end._

The members of the genus _Armadillidium_ are more likely to be
confounded, by the uninitiated, with the "Pill-millipedes" than with
other Woodlice. Excepting _Cylisticus_ (which has long pointed tail
appendages) no other British forms have the power of rolling themselves
up into a complete ball. The very arched body is characteristic of
_Armadillidium_, and so is the groove into which the basal joints of
the antennæ fit when the creatures curl up.

The first two abdominal appendages only are provided with air-tubes.

=Armadillidium nasatum= Budde-Lund. PLATE XXII.

  1885  _Armadillidium nasatum_ Budde-Lund (8), p. 51.
  1892  _Armadillidium nasatum_ Dollfus (14), p. 10, fig. 12.
  1899  _Armadillidium nasatum_ Norman (misprinted _Porcellidium_) (49),
         p. 57. pl. VI., figs. 5-8.

_Armadillidium nasatum_ has a narrow but very prominent frontal lobe,
which is almost square and curves somewhat upwards and backwards. The
joints of the flagellum are approximately equal, and are together of
the same length as the last peduncular joint.

The telson is as long as it is broad at the base, and tapers to a
roundish point, while its sides are slightly incurved.

[Illustration: FIG. 56.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Armadillidium nasatum_.]

The outer divisions of the tail appendages are considerably longer than
broad, and are more or less paddle-shaped.

It will be noticed that the slope from thorax to telson is more gentle
than in the common species, _Armadillidium vulgare_, and the first
thoracic segment is not so greatly developed. Consequently the species
which we are considering does not produce a perfect sphere, and the
antennæ are not hidden when it rolls up. It is interesting to compare
this species with _Cylisticus convexus_. The surface of the body is
smooth, and its colour is a delicate brownish grey with more or less
distinct rows of darker markings.

_BRITISH LOCALITIES:--_

  _England_: Maldon; (W.M.W. from R.M.): Bluebell Hill, Maidstone
     (W.M.W.); Clifton, banks of the Avon; (W.M.W. from J.T.C. 1900):
     Leigh Woods, Clifton; Tunbridge Wells; South Devon; (Stebbing in
     49); Cheddar Cliffs, Somerset; (Norman, 49).

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; (28): Spain; (12): Italy; (23).

=Armadillidium vulgare= Latreille. PLATE XXIII.

  1804   _Armadillo vulgaris_ Latreille (37), p. 48.
  1804   _Armadillo variegatus_ Latreille (37).
  1853   _Armadillo ater_ Schnitzler (65), p. 48.
  1816   _Armadillo maculatus_ Risso (56), p. 158.
  1818   _Armadillo pillularis_ Say (62), p. 432.
  1825   _Armadillo pustulosus_ Dermarest (11), p. 323, pl. XLIX.
  1830-4 _Armadillidium commutatum_ Brandt and Ratzeburg (4), p. 81,
          pl. XIII., fig. 123.
  1833   _Armadillidium zenckeri_ Brandt (3), p. 185.
  1839   _Armadillo trivialis_ Koch (34), part 28, pl. XIV.
  1898   _Armadillidium vulgare_ Sars (59), p. 189, pl. LXXXII.

The common pill woodlouse is _Armadillidium vulgare_. Its frontal
lobe is not large, though it is broad, while its margin where it
joins the head is rounded and slightly recurved. The proximal joint
of the flagellum is somewhat the shorter and the two together, as in
_Armadillidium nasatum_, are of about the same length as the last joint
of the peduncle.

The telson has the form of a triangle with the angles truncated and is
about as long as it is broad at the base. The outer divisions of the
tail appendages are considerably broader than they are long.

The species can roll itself up into a very perfect sphere, and when
it assumes this form its antennæ are hidden beneath the much expanded
lateral plates of the first thoracic segment.

[Illustration: FIG. 57.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Armadillidium vulgare_.]

The body is smooth, shiny, and strongly arched. Its colour varies very
considerably, generally it is of a slaty-grey, but yellow markings are
often present to a greater or less extent. In a specimen before us
(from Bluebell Hill, Maidstone) the head is of a uniform dark grey,
the sides of the thorax are yellow, while the back is mottled with the
same colour. The abdomen, including the telson, is also yellow with the
exception only of the tail appendages, which are dark grey.

_BRITISH LOCALITIES:--_

  _England_: Warley; (W.M.W): Maldon; (W.M.W. from R.M.):
     Brightlingsea; Hanwell; Mortlake; Bluebell Hill, Maidstone;
     Langley; Skirmett; Pamber Forest; Kingston-on-Soar; Ipswich;
     (W.M.W.); Lynmouth; (W.M.W. from J.T.C.)

  _Scotland_: (Scott, 68.)

  _Ireland_: Ardrahan; (Norman, 50): Borris, Co. Carlow; Glandare,
     Terneay, Co. Cork; Courtstown, Co. Wexford; Cappagh, Co.
     Waterford; Castel, Co. Tipperary; (R.F.S.)

_FOREIGN DISTRIBUTION:--_

  _Europe_: Throughout; (23).

  _Asia_: Damascus; (23).

  _Africa_: Algeria; (23).

  _Atlantic Isles_: (23).

  _America_: North and South; (23).

  _Australia_: Melbourne (64 quoting Budde-Lund); New Zealand; (23).

=Armadillidium pulchellum= Zencker. PLATE XXIV.

  1799  _Oniscus pulchellus_ Zencker (78) (quoted by Koch in Panzer),
         part 62, pl. XXI.
  1833  _Armadillidium pulchellum_ Brandt (3), p. 188.
  1861  _Armadillo maculatus_ Sill (69), p. 5.
  1870  _Armadillidium pictum_ Plateau (not Brandt) (55), p. 116.
  1898  _Armadillidium pulchellum_ Sars (59), p. 191, pl. LXXXIII.,
         fig. 4.

The smallest British species is _Armadillidium pulchellum_. The frontal
lobe projects so as to make the head somewhat triangular. The antennæ
are very short and the distal joint of the flagellum is three times the
length of the other, while the two together are not as long as the last
peduncular joint.

[Illustration: FIG. 58.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Armadillidium pulchellum_.]

The telson is truncated at the end so that it is by no means as long as
it is broad at the base, and the outer divisions of the tail appendages
are in similar proportion.

The colour of the body (which is smooth) is dark brown with four
important series of light patches running down the back and less marked
variegations between them.

_BRITISH LOCALITIES:--_

  _England_: Matlock; (T.R.R.S.) Arnside; Westmorland (Brady, 50a).

  _Ireland_: Ballymote, (Irish Nat., May, 1901), Sligo; (Scharff).

_FOREIGN DISTRIBUTION:--_

  _Europe_: Vosges; Switzerland; Pyrenees; (23): Forest de Soignes;
     Belgium; (14).

=Armadillidium depressum= Brandt. PLATE XXV.

  1833  _Armadillidium depressum_ Brandt (3), p. 82. pl. XII.,
         figs, 4, 5, 6, C, D.
  1892  _Armadillidium depressum_ Dollfus (14), p. 17-18.

The frontal lobe in _Armadillidium depressum_ is very prominent and
much recurved. The antennæ are fairly long and while the two joints
of the flagellum are nearly equal they are together not so long as
the last peduncular joint.

[Illustration: FIG. 59.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE
ANTENNA OF _Armadillidium depressum_.]

The telson is slightly longer than it is broad at the base, and its
sides are incurved. As in _Armadillidium vulgare_ and _Armadillidium
pulchellum_ the outer divisions of the tail appendages are broader
than they are long.

The body is flatter than in the other species and bears tubercles; its
colour is a slate-grey with yellowish markings. The first thoracic
segment is well developed and the head appears as if almost completely
imbedded in it.

_BRITISH LOCALITIES:--_

  _England_: Clifton, banks of the Avon; (W.M.W. from J.T.C., 1900):
     Shirehampton, near Bristol; (Stebbing in 49): Clifton; (Dollfus
     from Miers 14).

_FOREIGN DISTRIBUTION:--_

  _Europe_: France; Italy; (25): Asia Minor; (14, quoting Brandt).

=Distribution of Species.= There are not sufficient records at present
to enable us to draw any conclusions as to the general distribution of
Woodlice in the British Isles, but it is hoped that more attention will
be given to these creatures, and that before long there may be other
material available.

=Conclusion.= At the beginning it was mentioned that the present work
grew out of an investigation into the fauna of Essex, and in order
to show what may be expected when places are explored in which no
collecting has been done, we may briefly indicate the results which we
obtained in the county in question.

It was not long before a species new to Britain--to wit, _Porcellio
ratzeburgii_--was found (74). This discovery was mentioned by Mr.
Stebbing in the _Victoria County History of Essex_ (p. 71), and he
prophesied that most of the British species then would be met with in
the county. We may safely claim to have shown that his prediction was
true, for we have been able to record in the preceding pages no less
than sixteen other species, as will be seen from the following lists:--

_WOODLICE RECORDED FROM ESSEX._

  1. _Ligia oceanica_
  2. _Ligidium hypnorum_
  3. _Trichoniscus pusillus_
  4. _Trichoniscus roseus_
  5. _Haplophthalmus danicus_
  6. _Oniscus asellus_
  7. _Philoscia muscorum_
  8. _Platyarthrus hoffmannseggii_
  9. _Porcellio scaber_
  10. _Porcellio pictus_
  11. _Porcellio dilatatus_
  12. _Porcellio laevis_
  13. _Porcellio ratzeburgii_
  14. _Metoponorthus pruinosus_
  15. _Cylisticus convexus_
  16. _Armadillidium nasatum_
  17. _Armadillidium vulgare_

Of these _Ligidium hypnorum_ calls for special mention, as it had not
been found in this country since Mr. Stebbing discovered it in Surrey
in 1873. Several of the Porcellios and _Cylisticus convexus_ have been
met with in but few places, and the same may be said of _Armadillidium
nasatum_.

Of the British species not as yet found in Essex _Trichoniscus vividus_
has at present only been recorded from Ireland; _Philoscia couchii_ and
_Armadillidium depressum_ have not been collected except in the extreme
south west of England, while _Metoponorthus cingendus_ has hitherto
only been noticed in Devonshire and Ireland. The other four species,
with the exception of _Porcellio rathkei_, which is well distributed
in west Middlesex (and might have been expected to occur in Essex),
are still rare. In fact, for _Trichoniscoides albidus_ but two British
localities are known; for _Haplophthalmus mengii_ three (two in England
and one in Ireland); while _Armadillidium pulchellum_ has only been
recorded from two or three places.

In other counties quite as satisfactory results were obtained as in
Essex--a systematic search in Buckinghamshire brought to light at Eton
three species which at the time had not been recorded from the British
Isles, while in Middlesex, no less than a dozen species were found at
Hanwell.

Since part of this contribution was printed our attention has been
drawn to some notes by the Rev. Canon Norman and Professor G. S. Brady
(50a). These bear out the remarks which have already been made, for
among the species found by Professor Brady in the north of England
were _Trichoniscoides albidus_, _Haplophthalmus mengii_, _Porcellio
rathkei_, and _Armadillidium pulchellum_. In one of Canon Norman's
previous papers (50--1903) he claims to have added the second species
to the British list, and in the notes in question a similar claim is
made with regard to the first and third. It should, however, be pointed
out that all three of them were found in Buckinghamshire in 1899 by Mr.
Webb, and that they were exhibited at the Nature Study Exhibition held
in London in August, 1902. A specimen of _Armadillidium pulchellum_
from Matlock was sent to us by the Rev. T. R. R. Stebbing in January,
1904, and was found, we understand, some considerable time previously.

It only remains for us to express our hearty thanks to the numerous
friends and correspondents who have given us their ready help. The
names of these have been printed in the text, but we would like to
mention more particularly Dr. Calman, of the British Museum (Natural
History), Monsieur Adrian Dollfus, Mr. Roland Matthams, the Rev. Canon
Norman, Dr. Scharff, the Rev. T. R. R. Stebbing, and Miss Willmott.


FOOTNOTES:

[1] "The Non-Marine Molluscs of Essex," by Wilfred Mark Webb; ESSEX
NATURALIST, Vol. x. (1897), pp. 27-48 and 65-81.

[2] The numbers in brackets refer to papers mentioned in the
Bibliography at the end.

[3] It should be pointed out that the methylated spirit now sold in the
shops contains mineral naphtha and goes milky on the addition of water.
Permission can be obtained from Somerset House to buy what is still
called "ordinary methylated spirit," but at present five gallons has to
be purchased at one time.




BIBLIOGRAPHY.


Explanation of the initials given in the text:--

  B.M.--Specimens in the British Museum (Natural History).
  J.T.C.--John Thomas Carrington.
  J.A.M.--James A. Murie.
  R.M.--Roland Matthams.
  R.F.S.--R. F. Scharff.
  C.S.--Charles Sillem.
  T.R.R.S.--The Rev. Thomas R. R. Stebbing.
  W.M.W.--Wilfred Mark Webb.
  R.W.--R. Welch.

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  (14) DOLLFUS, A.: "Le Genre Armadillidium." _Feu. des Jeunes
         Naturalistes_, Ser. 3. May 1892.

  (15) DOLLFUS, A.: "Catalogue raisonné des Isopodes terrestres de
         l'Espagne." Premier supplement, _Ann. Soc. Espan. Hist. Nat._
         Vol. XXII. (1893), pp. 47-51.

  (16) DOLLFUS, A.: "Isopodes Terrestres in 'Voyage de M. Ch.
         Allmand aux Iles Canaries.'" _Mem. Soc. Zool. de France._
         Vol. VI. (1893), p. 46.

  (17) DOLLFUS, A.: "Sur la Distribution Geographique des
         Armadilliens en Europe." _Compte-Rendu troisieme Congres.
         Internal. de Zool._ Leyden, Sept. 1895 (1896), pp. 356-358.

  (18) DOLLFUS, A.: "Les Isopodes terrestres du Nord de l'Afrique du
         Cap. Blanc a Tripoli." _Mem. Soc. Zool. Trans._ Vol. IX.
        (1896), pp. 523-553.

  (19) DOLLFUS, A.: _Crustacés Isopodes de la Sicile._ 1896.

  (20) DOLLFUS, A.: "On West Indian Isopod Crustaceans." _Proc.
         Zool. Soc. Lond._ 1896, pp. 388-400.

  (21) DOLLFUS, A.: "Tableau Iconographique des _Philoscia_
         d'Europe." _Feu. des Jeun. Natural._ Ser. 3, 1897, pp. 70-73
         and 91-95.

  (22) DOLLFUS, A.: "Land Isopods der Balkan region." _Wissenschaft
         Mittheilung aus Bosnien und der Hercegovina._ Vol. IV. (1896).

  (23) DOLLFUS, A.: "Les Crustacés Isopodes Terrestres à grande
         dispersion," _Feu des Jeun. Natural._ Ser. 3 (Oct. 1897).

  (24) DOLLFUS, A.: "Sur la Distribution Geographique des Isopodes
         Terrestres dans l'Afrique Septentrional du Senegal à Obock."
         _Proc. Inter. Congres. Zool._ Cambridge, 1898, pp. 249-259.

  (25) DOLLFUS, A.: "Catalogue des Crustacés Isopodes Terrestres de
         France." _Feu. des Jeun. Natural._ Ser. 3 (October 1899).

  (26) FABRICIUS, J.C.: _Entomologia systematica._ Vol. II.,
         Hauniae, 1793.

  (27) FABRICIUS, J. C.: Supplement to the last, 1798.

  (28) FERNIE, Dr.: _Animal Simples_, 1899.

  (29) FITCH, Asa.: _Noxious Insects of New York._ Albany, 1856.

  (30) GUERIN, F.E.: "Sur _Porcellio Poeyi_." _Ann. Sci. Soc. Entom.
         de France._ Vol. VI. (Paris, 1837, in Bull. ent., page 6).

  (31) HELLER, C.: _Reise der Novara; Crustacea._ 1865.

  (32) KINAHAN, J.R.: "Analysis of certain genera of terrestrial
         Isopoda." _Nat. Hist. Rev._ Vol. IV. (1857).

  (33) KINAHAN, J.R.: "On the genera _Philoscia_, _Itea_ and
         _Philougria_." _Nat. Hist. Rev._ Vol. V. 1858.

  (34) KOCH, C.L.: _Deutschlands Crustaceen, Myriapoden and
         Arachniden._ Regensburg, 1835-1844.

         Koch's descriptions and figures were published in _Deutschlands
          Crustaceen_ and appeared also in Panzer's _Faunæ Insectorum
          Germanicæ_ continued by Herrich-Schäffer (which see). The
          number of the parts of the latter which correspond to those
          of the former are placed in square brackets after them in the
          list here given. Part 6 (1836) [139]; Part 22 (1838) [162];
          Part 28 (1839) [178]; Part 34 (1840) [180]; Part 36 (1844)
          [186]. Some of the dates quoted will be found to differ from
          those usually given (in Budde-Lund (8, p. 7) for instance),
          and printed on the parts of the copy in the Zoological
          Society's Library. Our authority for this change is Mr. C. D.
          Sherborne, who bases his dates upon reviews which he has
          discovered.

  (35) KOCH, C. L.: _System der Myriapoden mit den Verzeichnissen
         und Berichtigungen zu Deutschlands Crustaceen, Myriapoden und
         Arachniden._ Regensburg, 1847.

  (36) LAMARCK, J. B.: _Histoire naturelle des animaux sans
         vertébres._ Vol. V., 1818.

  (37) LATREILLE, P. A.: _Histoire Naturelle des Crustacés et des
         Insectes._ Vol. VII., Paris, 1804.

  (38) LEACH, W. E.: "Tabular view of the external characters of
         four classes of animals, which Linné arranged under Insectes."
         _Trans. Linn. Soc. Lond._ Vol. XI., 1815.

  (39) LEREBOULLET, A.: "Memoire sur les Crustacés de la famille des
         Cloportides qui habitent les environs de Strasbourg." _Mem. Soc.
         Mus. Hist. Nat. Strasbourg._ Vol. IV., 1853, pp. 130, pl. X.

  (40) LEUCKART, R.: _Verzeichnisz der zur Fauna Helgolands
         gehörenden wirbellosen Seethiere._ Braunsweig, 1847.

  (41) LINNÉ, C.: _Fauna Suecica._ First edition, Holmiæ, 1746.

  (42) LINNÉ, C.: _Fauna Suecica._ Second edition, Holmiæ, 1761.

  (43) LINNÉ, C.: _Systema Naturae_, ed. 12, 1767.

  (44) MIERS, E. J.: "Catalogue of New Zealand Crustacea." _Ann.
         Mag. Nat. Hist., Ser. 4._, Vol. XVII., 1876.

  (45) MIERS, E. J.: "On a collection of Crustacea (Decapoda and
         Isopoda), chiefly from South America." _Proc. Zool. Soc._,
         1877, p. 653-678.

  (46) MILNE-EDWARDS, H.: _Histoire naturelle des Crustacés._ Vol.
         III. Paris, 1840.

  (47) NICHOLSON and LYDDEKER: _Manual of Palæontology_, 1889, Vol.
         II., p. 559.

  (48) NORMAN, A. M.: "Note on the discovery of _Ligidium agile_,
         Persoon (_Zia saundersii_ Stebbing)." _Ann. Mag. Nat. Hist.
         Ser. 4_, Vol. XI., p. 419.

  (49) NORMAN, A. M.: "British Land Isopoda." _Ann. Mag. Nat. Hist.
         (Ser. 7)_, Vol. III. (1899), pp. 71-78, pl. VI.

  (50) NORMAN, A. M.: Continuation of the last. Vol. XI., 1903, pp.
         309-372.

  (50a) NORMAN, A.M.: and BRADY C.S.: "British Land Isopoda." Second
         Supplement _Ann. Mag. Nat. Hist. (Ser. 7)_, Vol. XIV. (1904),
         pp. 449-450.

  (51) PANZER, G. W. F.: _Faunæ Insectorum Germanicæ initia, oder
         Deutschlands Insecten._ Parts 1-110, Nurnberg, 1793-1813.
        (See Koch.)

  (52) PANZER, G. W. F.: Continuation by Herrich-Schäffer, Parts
         111-190, 1829-1844. (See Koch.)

  (53) PARFITT, E.: "The Fauna of Devon." Sessile-Eyed Crustacea.
         _Trans. Devon Assoc. Sci._, Sept. 1873.

  (54) PERSOON: No paper upon Woodlice by this author is known, but
         he is quoted in Panzer's _Deutschlands Insecten_ (51), which
         see.

  (55) PLATEAU, F.: "Crustacés Isopodes Terrestres." _Bull. Acad.
         Roy. de Belgique, Ser. 2._, Vol. XXIX., No. 2 (1870), p. 112.

  (56) RISSO, A.: _Histoire Naturelle des Crustacés des environs de
         Nice._ Paris, 1816.

  (57) ROBERTSON, D.: "Catalogue of the Amphipoda and Isopoda of
         the Firth of Clyde." _Trans. Nat. Hist. Soc. Glasgow_, Vol. II.
         (1888), pp. 9-99.

  (58) ROULE, LOUIS: "Etudes sur le Development de Crustacés." _Ann.
         Sci. Nat._, Vol. XVIII. (1895), pp. 1-156, pls. I.-X.

  (59) SARS, G. O.: _An account of the Crustacea of Norway._ Vol.
         II., 1896-1899.

  (60) SAUSSURE, H. de: "Diagnoses de quelques crustacés nouveaux
         des Antilles et du Mexique." _Rev. et Mag. de Zool. (Ser. 2)_,
         Vol. IX. (1857), pp. 304-308.

  (61) SAVIGNY, J. C., and AUDOUIN, V.: _Description de l'Egypte._
         Vol. XXII., 1827.

  (62) SAY, T.: "An account of the Crustacea of the United States."
         _J. Acad. Nat. Sci. Philadelphia_, Vol. I., pt. II., 1818.

  (63) SCHARFF, R. F.: "The Irish Woodlice." _Irish Naturalist_,
         Vol. III., 1894, pp. 4-7 and 25-29, pl. II.

  (64) SCHARFF, R. F.: "The Woodlice of Co. Carlow." _Irish
         Naturalist_, 1895, p. 319.

  (65) SCHNITZLER, H. J.: _De Oniscineis agri Bonnensis._ (Thesis.),
         Cologne, 1853.

  (66) SCHOBL, J.: "_Typhloniscus_, eine neue blinde Gattung der
         Crustacea Isopoda." _Sitzungsberichte der math. naturw. Acad.
         Wiss. Wien._ Vol. XL. (1860), pp. 279-330.

  (67) SCOPOLI, J. A.: _Entomologia Carniolica._ Vindibonæ, 1763.

  (68) SCOTT, T.: "The Land and Freshwater Crustacea of the District
         around Edinburgh." _Proc. R. Phys. S. Edin._, Vol. XI.
        (1890-91), p. 75.

  (68a) SCOTT, T.: _British Association Hand Book on the Natural
         History of Glasgow._ 1901; _Isopoda_, pp. 335 and 336.

  (69) SILL, VICTOR: "Beitrag zur Kentniss der Crustaceen,
         Arachniden and Myriapoden Siebenburgens." _Verhandl. u.
         Mittheil. des Siebenburghischen Ver. für Naturwiss. zu
         Hermannstadt_, Vol. XII. (1861), p. 1-11.

  (70) STEBBING, T. R. R.: "On a Crustacean of the Genus Zia." _Ann.
         Mag. Nat. Hist. Ser. 4._, Vol. XI. (1873).

  (71) STEBBING, T. R. R.: _The Victoria County History of Essex_
         (1903); Crustacea, pp. 27-28.

  (71a) STEBBING, T. R. R.: _The Victoria County History of
         Buckinghamshire_ (1905); Crustacea.

  (72) VEJDOVSKYF: "Zur Morphologie der Antennen und Schalendruse
         der Crustaceen." _Zeit. Wiss. Zool._, Vol. LXIX., p. 378.

  (73) VERHOEF, K. W.: "Ueber Palæarktische Isopoden." _Zool. Anz._,
         Vol. XXIV.

  (74) WEBB, WILFRED MARK: "The occurrence in Essex of a species
         of Woodlouse (Isopoda) new to Britain (_Porcellio ratzeburgii_,
         Brandt)." _Essex Naturalist_, Vol. XI. (1899), p. 127.

  (75) WEBB, WILFRED MARK: "Notes on Woodlice" (Including extracts
         from a paper read before the North London Natural History
         Society by James B. Casserley). _Science Gossip_, Vol. VI.,
         New Series (1900), pp. 295-296.

  (76) WEBER, MAX.: "Uber einige neue Isopoden der Niederlandischen
         Fauna." _Tijdschr der Niederland Dierk veren_, Vol. V. (1881),
         pp. 167-196, pl. V.

  (77) ZADDACH, E. G.: _Synopses crustaceorum Prussicorum prodromus
         Regiomonti_, 1844.

  (78) ZENKER, C. D.: No paper upon woodlice by this author is
         known, but he is quoted in Panzer's _Deutschlands Insecten_
         (51), which see.

  (79) ZITTEL, K. A. von: _Textbook of Palæontology_. English
         Translation 1900, p. 668.




INDEX.


  Abdomen, 2, =2=

  Aegidae, 2

  Air cavities, in abdominal appendages, 31

  Air tubes, 1, 6, 31, 33, 34, 35, 36, 37, 39

  _albidus, Trichoniscoides_, description of, 25

  Alcohol, 16

  Antennae, large, 2, =3=

      "     smaller, 2, =3=

  Alimentary canal, 6, =7=

  Ants, 31

    "   wood, 14

  Anus, 31, inset facing =10=

  Appendages, 2

        "     abdominal, 5, =6=

  _Archaeoniscus brodiei_, 2

  Armadillidæ, 17

        "      characters of, 18, 40

  _Armadillidium_, 15, 38

          "      _commutatum_, 41

          "      _depressum_, 44

          "            "        description of, 43

          "            "        flagellum of, =43=

  _Armadillidium nasatum_, 41, 44, Plate xxii.

          "            "        description of, 40

          "            "        flagellum of, =40=

  _Armadillidium pictum_, 42

          "      _pulchellum_, 43, 44, 45, Plate xxxiv.

          "            "        description of, 42

          "            "        flagellum of, =42=

  _Armadillidium vulgare_, 15, 40, 43, 44, Plate xxiii.

       "           "            description of, 41

       "           "            flagellum of, =41=

       "           "            moulting of, 12, 13

       "         _zenckeri_, 41

  _Armadillo ater_, 41

       "     _maculatus_, 41, 42

       "     _pillularis_, 41

       "     _pustulosus_, 41

       "     _trivialis_, 41

       "     _variegatus_, 41

       "     _vulgaris_, 41

  Arthropoda, 1

  Arteries, 7, =7=

  _asellus, Oniscus_, description of, 27

  Avebury, Lord, 31


  Baden, Miocene of, 2

  Bate and Westwood, 17, 19, 30

  Blastoderm, 10

  Body cavity, 11, inset facing =10=

  Brady, Professor C. S., 45

  Branchial nephrocytes, 8

  British Association, 19

  Brood pouch, 4, =5=, 9

  Budde-Lund, 28


  Calman, Dr., 45

  Carpenter, 15

  Cells, nucleated, 10, inset facing =10=

  Cephalic nephrocytes, 8

  Cheslip, 15

  Chiselbob, 15

  Church louse, 16

  Cicatricula, 10, inset facing =10=

  _cingendus, Metoponorthus_, description of, 38

  Circulatory system, 6, 7

  Classification, 17

  Coal measures, 1

  Collection of Woodlice, methods of, 16

  Commissures, 8, =8=

  Conclusion, 43

  _convexus, Cylisticus_, description of,39

  _couchii, Philoscia_, description of, 30

  Crabs, land, 1

  Crustacea, 1

  Cud worm, 15, 16

  _Cylisticus_, 40

        "   characters of, 17, 18, 38

  _Cylisticus convexus_, 44, Plate xxi.

        "          "     description of, 39

        "          "     flagellum of, =39=

        "     _laevis_, 35, 39

  _Cymothoa oceanica_, 20


  _danicus, Haplophthalmus_, description of, 27

  _depressum, Armadillidium_, description of, 43

  Development, 9

  Digestive glands, 6, =7=

  _dilatatus, Porcellio_, description of, 33

  Distribution of species, 43

  Dollfus, Adrian, 45


  Economic considerations, 12

  Egg, 9, 10, =10=, =11=, inset facing =10=

   "   segmentation of, 11, inset facing =10=

  Embryo, 10, =11=

  Endoderm, 10, inset facing =10=

  Essex, Woodlice recorded from, 44

  Excretory organs, 7

  Exhibition of species new to Britain, 45

  Exmoor, woodlice and ants on, 14

  External structure, 2


  Flagellum, 3, =3=

  Food, 13, 14


  Ganglia, cerebral 8

  Geological history, 1

  Genera, 17

  Gill, 5, =5=

  Gills, 7, =6=

  _Glomeris marginata_, 15

  Grammar sows, 16

  Growth, time required for, 12

  Gullet, 6

  Gut, fore, inset facing =10=

   "   mid, inset facing =10=


  Habits, 12

  Hall, Miss Kate M., 31

  _Haplophthalmus_, 22

          "          characters of, 17, 18, 26

          "          _danicus_, 44, Plate viii.

          "               "      description of, 27

          "               "      flagellum of, =27=

          "          _elegans_, 26

          "          _mengii_, 44, 45, Plate vii.

          "              "       description of, 26

          "              "       flagellum of, =26=

  Head, 2, =2=, =3=

  Heart, 6, 7, =7=, 11

  Herefordshire, Old Red Sandstone, 1

  History, geological, 1

  _hoffmannseggii, Platyarthrus_, description of, 30

  Hog-louse, 15

  Hogs, little grey, 16

  Hydro-cyanic acid gas for destroying woodlice, 14

  _hypnorum, Ligidium_, description of, 21


  Insects, 1

  Intestine, 6, =7=

      "      formation of, in embryo, 10, 11

  Isle of Wight, Oligocene of, 2, Oolite of, 2

  Isopoda, 1, 19

  _Itea crassicornis_, 30

     "   _laevis_, 22

     "   _mengii_, 26

     "   _rosea_, 24

     "   _riparia_, 22

     "   _vivida_, 23


  Jurassic, Upper, 2


  Kinahan, Professor, 19, 28, 30

  Kitchenball, 15


  Labels, 16

  _laevis, Porcellio_, description of, 35

  _Ligia_, 21

      "    branchial nephrocytes, 8

      "    characters of, 17, 18, 19, 20

      "    _hypnorum_, 21

      "    _melanocephala_, 29

      "    _oceanica_, 44, Plate i.

      "        "       description of, 20

      "        "       excretory organs of, 7, 8

      "        "       flagellum of, 20, =20=

      "    _scopulorum_, 20

  Ligiae, 17

     "    characters of, 19

  Ligiidae, characters of, 17, 18, 19

  _Ligidium_, 19

      "       characters of, 17, 18, 21

      "       _hypnorum_, 44, Plate ii.

      "            "      description of, 21

      "            "      excretory organs of, 7

      "            "      in Surrey, 19

      "       _persoonii_, 21

  Lip, the lower, 4, =5=

   "   the upper, 4, =5=

  Lucre pig, 15

  Lugdor, 15


  Mandibles, 3, =4=

  Manure, from stables, favourable to woodlice, 14

  Maxillae, first, 3, =4=

     "      second, 3, =4=

     "      openings of excretory organs on second, 7

  Maxillipeds, 3, =4=

  _mengii, Haplophthalmus_, description of, 26

  Mesoderm, 10, inset facing =10=

  Methylated spirit, 16

  _Metoponorthus_, 21

         "          characters of, 18, 37

         "          _cingendus_, description of, 38, Plate xx.

         "                 "     flagellum of, =38=

         "          _pruinosus_, 44, Plate xix.

         "                "     description of, =37=

         "                "     flagellum of, 37

         "          _simplex_, 38

  Miocene, 2

  Middlesex, West, 35

  Millipede, pill, 15, 40

  Moult, 11

  Moulting, process of, 12, 13, 14

  Mouth appendages, 3, =4=

  _muscorum, Philoscia_, description of, 29


  Names, local, 15

  _nasatum, Armadillidium_, description of, 40

  Nephrocytes, branchial, 8

        "      cephalic, 8

  Nerve cord, 8, =8=

  Nervous system, 8

  Norman, Rev. Canon A. M., 25, 27, 45


  _oceanica, Ligia_, description of, 20

  Oenigen, Miocene of, 2

  Old-sows, 16

  Old women of the wood, little, 16

  Oligocene, 2

  Onisci, 17

     "    characters of, 27

  Oniscidae, 19

  _Oniscus_, 28

      "      branchial nephrocytes, 8

      "      characters of, 17, 18, 27

      "      _agilis_, 21

      "      _asellus_, 4, 15, 28, 44, Plate ix.

  _Oniscus asellus_, Albino in Epping Forest, 28

       "       "     description of, 27

       "       "     excretory organs of, 8

       "       "     flagellum of, =28=

       "       "     young examples of, 28

       "   _convexus_, 39

       "   _fossor_, 19, 28

       "   _granulatus_, 32

       "   _murarius_, 27

       "   _muscorum_, 29

       "   _oceanicus_, 20

       "   _pulchellum_, 42

       "   _sylvestris_, 29

  Oolite, 2

  Ovaries, 8, =8=

  Oviducts, 8, =8=


  Palmer, 16

  Penis, 9, =9=

  Peduncle, 3, =3=

  _Philoscia_, 21, 28

       "       characters of, 17, 18, 29

       "       _couchii_, 44, Plate xi.

       "           "     description of, 30

       "           "     flagellum of, =30=

       "       _marmorata_, 29

       "       _muscorum_, 21, 44, Plate x.

       "            "      description of, 20

       "            "      flagellum of, =29=

  _Philougria celer_, 29

       "        _riparia_, 22

       "        _rosea_, 24

       "        _vivida_, 23

  Physicians, college of, rules for preparing woodlice for
       medicinal use, 18

  _pictus, Porcellio_, description of, 33

  Pill millipede, 15, 40

  _Platyarthrus_, 22

        "         characters of, 17, 18, 39

        "         _hoffmannseggii_, 44, Plate xii.

        "               "          description of, 30

        "               "          flagellum of, =31=

  _Porcellio_, 6, 28, 38

        "      characters of, 7, 18, 32

        "      _armadilloides_, 39

        "      _asper_, 32

        "      _aztecus_, 35

        "      _brandtii_, 32

        "      _cinerascens_, 35

        "      _cingendus_, 38

        "      _cotillae_, 35

        "      _cubensis_, 35

        "      _degeerii_, 35

        "      _dilatatus_, 34, 44, Plate xv.

        "           "       description of, 33

        "           "       flagellum of, =34=

        "       _dubius_, 32, 33

        "       _ferrugineus_, 34

        "       _flavipes_, 35

        "       _flavo-vittatus_, 37

        "       _frontalis_, 37

        "       _graniger_, 32

        "       _laevis_, 39, 44, Plate xvii.

        "           "     description of, 35

        "           "     flagellum of, =35=

        "       _lugubris_, 36

        "       _maculicornis_, 37

        "       _melanocephalus_, 33

        "       _mexicanus_, 35

        "       _mixtus_, 33

        "       _montezumae_, 32

        "       _musculus_, 35

        "       _nemorensis_, 36

        "       _nigra_, 32

        "       _paulensis_, 32

        "       _pictus_, 34, 44, Plate xiv.

        "       description of, 33

        "       flagellum of, =33=

        "       _poeyi_, 35

        "       _pruinosus_, 37

        "       _quercum_, 36

        "       _rathkei_, 35, 36, 44, 45

        "           "      description of, 34, Plate xvi.

        "           "      flagellum of, =35=

        "       _ratzeburgii_, 44, Plate xviii.

        "            "         description of, 36

        "            "         flagellum of, =36=

        "       _scaber_, 28, 44, Plate xiii.

        "           "     description of, 32

        "       _scaber_, development of, 9

        "           "     flagellum of, 32

        "           "     Milne Edwards, 33

        "       _spinifrons_, 39

        "       _striatus_, 34

        "       _sumichtasti_, 35

        "       _syriacus_, 35

        "       _tetramoerus_, 34

        "       _trilineatus_, 34

        "       _trivittatus_, 34

        "       _truncatus_, 37

        "       _urbicus_, 35

  _Porcellionides_, Miers, 37

  Preservation of Woodlice, methods of, 16

  Pro-ectoderm, 10, inset facing =10=

  Pro-endoderm, 10, inset facing =10=

  Protoplasm, formative, 10

  _pruinosus, Metoponorthus_, description of, 37

  pseudotracheae, 31

  _pulchellum, Armadillidium_, description of, 42

  _pusillus, Trichoniscus_, description of, 22

  Purbeck Beds, 2


  Quay-louse, 20

  Quay lowders, 20


  _rathkei, Porcellio_, description of, 34

  _ratzeburgii, Porcellio_, description of, 36

  Reproductive organs, 8, =8=, =9=

  _roseus, Trichoniscus_, description of, 24

  Roule, Professor Louis, 9


  Sandstone, old red, 1

  Sars, Professor G. O., 17, 23

  _scaber, Porcellio_, description of, 32

  Scharff, Dr. R. F., 17, 19, 23, 45

  Seminal reservoir, 9, =9=

  Socchetre, 16

  Sow bug, 15

  Species, distribution of, 43

  St. Anthony's hogs, 16

  Stebbing, the Rev. T. R. R., 19, 21, 35, 44, 45

  Swanley Horticultural College, 14


  Tertiary deposits, 2

  Testes, 9, =9=

  Thorax, 2, 3

  Thrush louse, 15

  Tiggyhog, 15

  Tracheae, 6, 31

  Trichoniscidæ, characters of, 18, 22

  _Trichoniscoides_, 21, 22, 26

       "             characters of, 17, 18, 25

       "             _albidus_, 44, 45

       "              "    description of, 25

       "              "    flagellum of, =25=

  _Trichoniscus_, 21, 22, 26

       "          characters of, 17, 18, 22

       "          _pusillus_, 22, 23, 24, 25, 44, Plate iii.

       "               "      description of, 22

       "               "      flagellum of, =23=

       "           _pygmaeus_, description of, 23

       "           _roseus_, 23, 25, 44, Plate v.

       "               "     description of, 24

       "               "     flagellum of, =24=

       "           _vividus_, 22, 25, 44, Plate iv.

       "                "     description of, 23

       "                "     flagellum of, =24=

  Tubes for specimens, 16

  _Typhloniscus steinii_, 30


  _vividus, Trichoniscus_, description of, 23

  _vulgare, Armadillidium_, description of, 41


  Walking legs, 4, 5

  Webb, Mr. Wilfred Mark, 20, 25, 26, 35, 36, 45

  Welsh names for Woodlice, 16

  Westwood, Bate and, 17, 19, 30

  White arsenic for destroying Woodlice, 14

  Willmott, Miss, 45

  Wood-ants, 15

  Woodlice, in captivity, 12

      "     methods for getting rid of, 24

      "     position of, 1

      "     storage of specimens, 16

      "     Welsh names for, 16

  Woodlouse, common, 4


  Yolk, food, 10, 11, inset facing =10=


  _Zia agilis_, 21

     "     _melanocephala_, 29
$




LIST OF PLATES.


                                                  PLATE

  _Ligia oceanica_ Linné                             I.

  _Ligidium hypnorum_ Cuvier                        II.

  _Trichoniscus pusillus_ Brandt                   III.

  _Trichoniscus vividus_ Koch                       IV.

  _Trichoniscus roseus_ Koch                         V.

  _Trichoniscoides albidus_ Budde-Lund              VI.

  _Haplophthalmus mengii_ Zaddach                  VII.

  _Haplophthalmus danicus_ Budde-Lund             VIII.

  _Oniscus asellus_ Linné                           IX.

  _Philoscia muscorum_ Scopoli                       X.

  _Philoscia couchii_ Kinahan                       XI.

  _Platyarthrus hoffmannseggii_ Brandt             XII.

  _Porcellio scabier_ Latreille                   XIII.

  _Porcellio pictus_ Brandt and Ratzeburg          XIV.

  _Porcellio dilatatus_ Brandt                      XV.

  _Porcellio rathkei_ Brandt                       XVI.

  _Porcellio laevis_ Latreille                    XVII.

  _Porcellio ratzeburgii_ Brandt                 XVIII.

  _Metoponorthus pruinosus_ Brandt                 XIX.

  _Metoponorthus cingendus_ Kinahan                 XX.

  _Cylisticus convexus_ De Geer                    XXI.

  _Armadillidium nasatum_ Budde-Lund              XXII.

  _Armadillidium vulgare_ Latreille              XXIII.

  _Armadillidium pulchellum_ Zencker              XXIV.

  _Armadillidium depressum_ Brandt                 XXV.

[Illustration: _PLATE I._

LIGIA OCEANICA Linné. THE QUAY-LOUSE.

_Length, two to three centimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE II._

LIGIDIUM HYPNORUM Cuvier.

_Length, nine millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE III._

TRICHONISCUS PUSILLUS Brandt.

_Length, four millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE IV._

TRICHONISCUS VIVIDUS Koch.

_Length, eight millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE V._

TRICHONISCUS ROSEUS Koch.

_Length, five millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE VI._

TRICHONISCOIDES ALBIDUS Budde-Lund.

_Length, four millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE VII._

HAPLOPHTHALMUS MENGII Zaddach.

_Length, three to four millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE VIII._

HAPLOPHTHALMUS DANICUS Budde-Lund.

_Length, three to four millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE IX._

ONISCUS ASELLUS Linné (The common slater).

_Length, sixteen millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE X._

PHILOSCIA MUSCORUM Scopoli.

_Length, nine millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE XI._

PHILOSCIA COUCHII Kinahan.

_Length, nine millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE XII._

PLATYARTHRUS HOFFMANNSEGGII Brandt.

_Length, three millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE XIII._

PORCELLIO SCABER Latreille.

_Length, fourteen millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE XIV._

PORCELLIO PICTUS Brandt and Ratzeburg.

_Length, thirteen millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE XV._

PORCELLIO DILATATUS Brandt.

_Length, fifteen millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE XVI._

PORCELLIO RATHKEI Brandt.

_Length, twelve millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE XVII._

PORCELLIO LAEVIS Latreille.

_Length, sixteen millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE XVIII._

PORCELLIO RATZEBURGII Brandt.

_Length, eleven millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE XIX._

METOPONORTHUS PRUINOSUS Brandt.

_Length, nine millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE XX._

METOPONORTHUS CINGENDUS Kinahan.

_Length, six millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE XXI._

CYLISTICUS CONVEXUS De Geer.

_Length, twelve millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE XXII._

ARMADILLIDIUM NASATUM Budde-Lund.

_Length, fifteen millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE XXIII._

ARMADILLIDIUM VULGARE Latreille.

_Length, fifteen millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE XXIV._

ARMADILLIDIUM PULCHELLUM Zencker.

_Length, five millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]

[Illustration: _PLATE XXV._

ARMADILLIDIUM DEPRESSUM Brandt.

_Length, fifteen millimetres._

Charles Sillem, del. ad nat. F. W. Reader, sculpt.]


       *       *       *       *       *


Transcriber's Notes

Obvious typographical errors have been corrected. Inconsistent
accents, punctuation, and hyphenation are as in the original text.

The "æ" ligature is used interchangeably with "ae" throughout.

Some taxonomic names may have changed since 1906.

The following misprints and misspellings have been noted or corrected:

CONTENTS:-
Page  vii: "Family--Ligidæ " changed to "Family--Ligiidæ".
Page  vii: "Haplopthalmus mengii" changed to "Haplophthalmus mengii".
Page viii: "Armydillidium vulgare" changed to "Armadillidium vulgare".

MAIN PART OF BOOK:-
Page  2: "Aegidae is found" changed to "Aegidae which is found".
Page 16: "naptha" changed to "naphtha" in footnote.
Page 28: "Thornsharn" changed to "Thorsharn".
Page 29: "Philoscia marmorala" changed to "Philoscia marmorata".
At the end of the following lines, there is a missing page reference:
  Page 30: "1868  _Philoscia couchii_ Bate and Westwood (1), p."
  Page 33: "1868  _Porcellio pictus_ Bate and Westwood (1), p."
  Page 33: "1868  _Porcellio dilatatus_ Bate and Westwood (1), p."

INDEX:-
Page 51: "Ligidae, characters of" changed to "Ligiidae, characters of".