FIG. 21.—THE MALE REPRODUCTORY ORGANS.(Oniscus asellus.)
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. Thebrood pouchhas already been described.
The male organs consist of sixtestesarranged in two pairs, each of which is provided with areservoir(see fig. 21). The efferent ducts from the two reservoirs unite at the base of the thorax to form a common duct (or "penis").
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) inPorcellio scaberand 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 theparent, 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 offood-yolk, on the outside of which theformative protoplasmis 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 thecicatricula. This is the only portion of the egg which divides and producesnucleated cells. It is these which gradually spread all over the surface of the food-yolk, forming a layer known as theblastoderm, 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—thepro-ectodermandpro-endoderm—takes place (see fig. 25) and rudiments of the first two pairs ofappendagesappear (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.
FIG. 22.—THE FERTILIZED EGG(Porcellio scaber), AFTER ROULE.FIG. 23.—THE FERTILIZED EGG SEEN IN SECTION(Porcellio scaber), AFTER ROULE.
FIG. 22.—THE FERTILIZED EGG(Porcellio scaber), AFTER ROULE.
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—theendoderm properand themesoderm(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 theintestine, 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 thetrue body cavitycharacteristic of animals above the level of the jelly fish, and in these spaces the blood ultimately circulates.
Pg 10 Plate LH TitleSURFACE VIEWS.Pg 10 Plate RH TitleOPTICAL SECTIONS.
Pg 10 Plate LH TitleSURFACE VIEWS.
Pg 10 Plate RH TitleOPTICAL SECTIONS.
FIG. 24.FIG. 25.
FIG. 24.
FIG. 25.
FIG. 26.FIG. 27.
FIG. 26.
FIG. 27.
FIG. 28.FIG. 29.
FIG. 28.
FIG. 29.
FIG. 30.FIG. 31.
FIG. 30.
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.
FIG. 32.—EMBRYO OF THE WOODLOUSE SHOWING THE THREE DIVISIONS OF THE INTESTINE SEPARATELY DEVELOPED (Porcellio scaber), AFTER ROULE.FIG. 33.—EMBRYO OF THE WOODLOUSE SHOWING TRACES OF THE SEGMENTS (Porcellio scaber), AFTER ROULE.
FIG. 32.—EMBRYO OF THE WOODLOUSE SHOWING THE THREE DIVISIONS OF THE INTESTINE SEPARATELY DEVELOPED (Porcellio scaber), AFTER ROULE.
FIG. 33.—EMBRYO OF THE WOODLOUSE SHOWING TRACES OF THE SEGMENTS (Porcellio scaber), AFTER ROULE.
In the last stages of the development the appendages become larger still, theheartmakes 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.
FIG. 34.—EMBRYO OF THE WOODLOUSE SHOWING TRACES OF THE SEGMENTS (Porcellio scaber), AFTER ROULE.
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 ofwalking 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 inArmadillidium vulgare. (See p. 13.)
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 isjust 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 ofArmadillidium 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 muchso 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 noArmadillidia, though other forms occurred under nine out of every ten stonesthat he turned over, and here the smaller species of ants also abounded. Close to stone wallsArmadillidiawere 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 asOniscus asellus. He calls the former, however, indiscriminately, "the common armadillo" (which is the old name for the pill-woodlice now known asArmadillidium), "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 anArmadillidium, 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 isArmadillidium 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 aselluswas 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 hisCrustacea 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.Family III.—Oniscidæ.Ligia.Oniscus.Ligidium.Philoscia.Platyarthrus.Porcellio.Metoponorthus.Cylisticus.
Family II.—Trichoniscidæ.Family IV.—Armadillidiiæ.Trichoniscus.Armadillidium.Trichoniscoides.Haplophthalmus.
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 appendageswholly visible; head without lateral lobesLigiidae.(1.)—Abdomen broad; body large; habitat,the sea-shoreLigia.(2.)—Abdomen narrow; habitat, wet mossLigidium.(B.)—Flagellum with less than 10 joints; head withsmall lateral lobes, tail appendages partlycoveredTrichoniscidæ.(3.)—Abdomen narrow; eyes compound;flagellum usually with more than 3jointsTrichoniscus.(4.)—Abdomen narrow; eyes simple or wanting;flagellum with 4 jointsTrichoniscoides.(5.)—Abdomen broad (comparatively); eyessimple; back with longitudinalridges; flagellum with 3 jointsHaplophthalmus.
Section II.—ONISCI.The Outer Divisions of the Tail Appendages Broader than the Inner.
(A.)—Tail appendages projecting when the animal iswalkingOniscidæ.(a.)—Unable to roll up into a complete ball.(6.)—Flagellum with 3 joints; abdomenbroad; head, with lateral lobesOniscus.(7.)—Flagellum with 3 joints; abdomennarrow; head without lateral lobesPhiloscia.(8.)—Flagellum with 1 joint; eyes wanting;abdomen broad; habitat, ant's nestsPlatyarthrus.(9.)—Flagellum with 2 joints; abdomenbroad; frontal lobe projectingPorcellio(10.)—Flagellum with 2 joints; abdomennarrowMetoponorthus.(b.)—Able to roll up into a complete ball.(11.)—Flagellum with 2 joints; antennaefolded together over the thorax whenthe animal is rolled up into a ballCylisticus.(B.)—Tail appendages not projecting when the animalwalkingArmadillidiidæ.(12.)—Flagellum with 2 joints; antennaehidden or carried at the sides of thehead when the animal is rolled upinto a ballArmadillidium.
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 foundLigidium hypnorumin 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—LIGIAFabricius, 1798 (27), p. 301.
Abdomen broad; body large; habitat, the sea-shore.
The genusLigiaagrees withLigidiumalone, 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 inLigiais, however, very many times bigger than inLigidiumand shows no abrupt decrease in the width of its segments when the abdomen is reached.
Ligia oceanicaLinné (The Quay-louse).Plate I.
1767Oniscus oceanicusLinné (43), p. 1061.1793Cymothoa oceanicaFabricius (26), p. 509.1815Ligia scopulorumLeach (38), p. 374.1868Ligia oceanicaBate and Westwood (1), p. 444.1898Ligia oceanicaSars (59), 156, pl. LXX.
FIG. 35.—FLAGELLUMAND LAST PEDUNCULARJOINT OF THE ANTENNAOFLigia oceanica.
There is but one British species ofLigia, 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 theOniscus oceanicusof Linnæus and lives on the sea shore, where it may be found at low tide beneath stones and rubbish in the crevices of timber.Ligiaforms 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.
It is worthy of mention that Mr. Webb, when in charge of the Marine Biological Station at Brightlingsea, examined a very large male specimen ofLigia 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—LIGIDIUMBrandt, 1833 (3), p. 173. Zia, Koch (34).
Abdomen narrow; habitat, wet moss.
InLigidiumthere 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 withTrichoniscus,Trichoniscoides,Philoscia, andMetoponorthus. In these, however, the flagellum has never more than seven joints, the tail appendages (as in all genera butLigiaandLigidium) are partially hidden by the last segment, and in all the four butPhilosciathere are lobes to the head.
FIG. 36.—FLAGELLUM AND LAST PEDUNCULARJOINT OF THE ANTENNAOFLigidium hypnorum.
Ligidium hypnorum, Cuvier.Plate II.
1792Oniscus hypnorumCuvier (9), pl. XXVI., figs. 3-5.1793Oniscus agilisPersoon, quoted by Koch in Panzer (51), part 5, pl. XXIV.1830Ligia hypnorumBosc (2), p. 179.1833Ligidium persooniiJ. F. Brandt (3), p. 174, pl. IV., figs. 6-7.1840Zia agilisKoch (34), part 34, pls. XXII. and XXIII.1844Ligidium personiiZaddach (77), p. 17.1853Ligidium personiiLereboullet (39), p. 14, pl. I., fig. 1, pl. II., figs. 20-31.1857Ligidium personiiKinahan (32), p. 275, pl. XXI., fig. 14, pl. XXII., fig. 9.1873Zia saundersiiStebbing (70), p. 286.1873Ligidium agileNorman (48), p. 419.1885Ligidium hypnorumBudde-Lund (8), p. 254.1898Ligidium hypnorumG. 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 hypnorumhas not been recorded from any other place in the British Islands.
As the name of the species implies, it lives in wet situations and in its turn connectsLigiawith the forms which inhabit drier places.Ligidium hypnorummight be mistaken forPhiloscia 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. FromLigia, 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—TRICHONISCUSBrandt, 1833 (3), p. 174.
Abdomen narrow; eyes compound; flagellum, usually with more than three joints.
InTrichoniscusthe flagellum may have from seven to four (rarely three) joints. As inTrichoniscoidesandHaplophthalmusthere 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 distinguishTrichoniscusfrom the two genera named, and fromPlatyarthrus, while its small size and the character of its tail-parts mark it out from all others.
Trichoniscus pusillusBrandt.Plate III.
1833Trichoniscus pusillusBrandt (3), p. 174, pl. IV., fig. 9.1838Itea ripariaKoch (34), part 22, pl. XVII.1844Itea lævisZaddach (77), p. 16.1857Philougria celerKinahan (32), p. 281, pl. XXII., figs. 1-4.1858Philougria ripariaKinahan (33), pp. 191 and 198, pl. XXIII., fig. 1.1868Philougria ripariaBate and Westwood (1), p. 456.1898Trichoniscus pusillusSars (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 pusillusis very much likeTrichoniscus vividusin 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 roseusis 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.
FIG. 37.—FLAGELLUMAND LAST PEDUNCULARJOINT OF THE ANTENNAOFTrichoniscuspusillus.
Professor Sars in hisCrustacea of Norway(p. 162) describes from Christiania, under the name ofTrichoniscus pygmæus, a still smaller species. As this may possibly be discovered in this country a brief comparison between it andTrichoniscus pusillusmay 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.
The body ofTrichoniscus pusillusis 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 WrighttesteBate 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).
1840Itea vividaKoch (34), part 34, pl. IV.1858Philougria vividaKinahan (33), pp. 197 and 198, pl. XXIII., fig. 2.1868Philougria vividaBate 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 likeTrichoniscus pusillusthough 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 inTrichoniscus vividuswhile in the other, as already pointedout, there are not more than four.
FIG. 38.—FLAGELLUMAND LAST PEDUNCULARJOINT OF THE ANTENNAOFTrichoniscusvividus.
The body is practically speaking smooth for it bears only very small tubercles, widely separated. InTrichoniscus vividusthe 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.
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 roseusKoch.Plate V.
1838Itea roseaKoch (34), part 122, pl. XVI.1858Philougria roseaKinahan (33), pp. 197 and 199, pl. XXIII., fig. 3.1858Philougria roseaBate and Westwood (1), p. 460.1898Trichoniscus roseusSars (59), p. 163, pl. LXXIII., fig. 1.
FIG. 39.—FLAGELLUMAND LAST PEDUNCULARJOINT OF THE ANTENNAOFTrichoniscus roseus.
The third British species ofTrichoniscusis 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 fromTrichoniscus pusillusby the larger size of its body, which is also comparatively broader, and fromTrichoniscus vividusby 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 roseusis to be looked for in old gardens.
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.