WOODLICE 7 



which can be distinguished from Oniscus asellus by its narrow 

 body and pretty marbled appearance is again usually found in 

 moist situations under rubbish heaps, damp moss and the carpet 

 of dead leaves in woods. 



A curious little, white, blind woodlouse is Platyarthrus hoffmann- 

 seggi. It is easily recognised by its broad flattened body up to 3-6 

 mm in length with denticulate edges to its segments and short, 

 stout antennae. This species occurs throughout the British Isles 

 and the rest of Europe, and its range extends into North Africa. It 

 is usually found in the nests of ants and the burrows of wood- 

 boring beetles. The species was described in 1833 by Brandt from 

 specimens taken in Prussia and was first noticed in Britain living 

 with several species of ants at Lulworth Cove, in 1859. Although it 

 has no eyes, Platyarthrus appears to be very averse to light and 

 quickly hides if disturbed. 



A New Zealand species of Trichoniscus^ T. commensalisy has in- 

 dependently evolved the same habit of associating with ants. It is 

 rather larger than Platyarthrus and is not quite white, but generally 

 marked with bands or patches of pale brown on a white ground. 

 Moreover, it is not blind but possesses fairly perfect eyes provided 

 with the normal amount of pigmentation. 



One of the largest and most common of woodlice is the garden 

 slater Oniscus asellus which reaches a length of 15 mm and about 

 half that width. Again the pleopods are without pseudotracheae, 

 but Oniscus spp. seem to wander in drier places than any of the 

 species mentioned previously. A number of species occur in the 

 family Porcellionidae, of which Porcellio scaber is the most usual 

 and has been recorded from all over the British Isles. It reaches a 

 size even larger than that of Oniscus asellus and is very variable in 

 colour, but it is usually a dark slaty grey with irregular lighter 

 markings. It can be recognised by the transverse rows of small 

 tubercles that cover the back of the head and body. This family is 

 better adapted to live in drier conditions than any of the preceding 

 and the pleopods bear well-developed pseudotracheae although a 

 certain amount of respiration also takes place through the integu- 

 ment of the body. 



To the same family belongs the remarkable desert woodlouse 

 Hemilepistus reaumuri which is not uncommon in North Africa and 



