HABITS AND LIFE-HISTORIES OF WOODLICE. 109
from above or from water beneath) not a single Woodlouse is to
be found. Knowing this fact, it is relatively easy, on observing
the state of decay and dryness of a tree trunk, to foretell whether
or not O. asellus is to be met with there. The same applies to
the finding of T. pusillus among decaying leaves, P. muscorum
among grass roots, and A. vulgare on chalky slopes.
The following observations on the habits of the individual
species which were made in the course of the collections, may
be of value and interest to the reader.
III. NATURAL HISTORY OF THE SELECTED SPECIES.
Trichoniscus pusillus. Abundant in very moist woodlands,
though frequently overlooked owing to its small size and dark
colouring, and liable to be mistaken for young Philoscia. They
favour the thick sodden layers of decaying leaves which lie
beneath the trees throughout the winter, and may almost
invariably be found on turning over these layers. During the
summer they live amongst the resultant leaf-mould beneath low-
growing bushes well shaded from the sun, or within rotting twigs.
They appear to be restricted to permanently damp situations
on the ground, in old, undisturbed woodland areas ; I have never
found them in trees or in the vicinity of houses, except in old
heaps of garden leaf-mould, carried there no doubt with the
leaves. Found all the year round. No sexual difference in
colouration or in size.
Porcellio dilatatus. This species does not occur frequently,
being largely or wholly restricted to the vicinity of cool glass-
houses and human dwellings, but where it does occur large
numbers are usually to be found within a small area. They
favour damp situations beneath seed-boxes and flower-pots
standing on the ground, and amongst straw, but they are not
to be found under leaves, and do not live in great heat or very
moist atmospheres. Found all the year round, but rarer in
winter ; commonest in March and April. No sexual difference
in colouration, but the males are slightly larger than the females.
Porcellio scaber. Very common, particularly beneath the
dry, loose bark of the vertical trunks of living trees, but by no
means confined to this situation. They sometimes inhabit damp
houses, and have on one occasion been met with in large numbers