HABITS AND LIFE-HISTORIES OF WOODLICE. 143
In the first place, however, a brief reference should be made
to their moulting processes, which take place at intervals through-
out life, and which, as in other Crustaceans, provide the means
of bodily growth in creatures possessing such hard, inelastic
exoskeletons in the adult state. The moulting of woodlice
takes place in two stages, the rear half of the integument being
cast off two or three days before the front half, the line of division
between the two being the junction of the fourth and fifth thoracic
segments. During these two stages the creatures become
quiescent and seek some remote corner, but in the intervening
period between the first and second process they become active,
and in the summer time especially they may often be seen in
this condition, with one half of their bodies moulted and pre-
senting a light, soft, moist appearance and the other half still
retaining the old integument, which is darker, hard and dry.
After the moult has been completed, however, the new integu-
ment soon hardens, and after a few hours' resting period the
creatures are able to try out their new armour plating and return
to their normal habits, sometimes feeding on their cast exuvia.
The younger members, having a less strongly calcified integu-
ment, complete the casting off process in a much shorter time.
This moulting period is of course a critical time for these animals,
and not all survive the process, some being attacked by their
fellows whilst in such a defenceless condition.
The pairing of these animals usually occurs yearly, during
the early Spring, and, it would seem, will suffice for at least two
successive broods, since I have kept specimens isolated for over
two years, and these have produced families of young in both
years without any possibility of pairing having taken place
during any part of this period. That the second year's brood
is not, in these cases at least, produced parthenogenetically is
proved by the fact that the young of these second year's broods
are of both sexes.
A moult occurs some weeks after the pairing, in the female,
and this heralds the commencement of the breeding period, for
as the old integument is cast off and the new one exposed, a series
of overlapping plates or "oostegites" is revealed, projecting
inwards from either side of the first five thoracic segments, and
forming a closed cavity or pouch on the ventral surface of the