148 THE ESSEX NATURALIST.
still continues to betray its belated appearance by remaining
for a long time a much lighter shade than the rest of the segments.
After the mother animal has liberated her young from her
brood pouch she appears to take no further interest in them, and
indeed will walk over them with complete unconcern, and if
deprived of food she will eat them. Her brood plates, having
fulfilled their purpose, now close in over the brood cavity and
adhere to the ventral body wall, and at the next moult, which
occurs some two to four weeks after the liberation of the young,
these brood plates are shed along with the old skin and the mother
reverts to the non-breeding condition, unless a second batch of
eggs have been developing meanwhile in the ovary, in which case
a new series of brood plates appears with the new integument.
The number of moults which the mother undergoes after her
breeding period appears to depend on the season of the year at
which she breeds ; if breeding occurs early in the year there may
follow as many as five moults before the approach of winter ; if
late in the year there may be only two moults.
During the Winter and early Spring moults of adult animals
appear to be rare and at infrequent intervals, and show no
regularity in their times of occurrence such as is seen during
breeding times. Similarly, the males show none of the regularity
of moults found in breeding females, some moulting only three
times a year, others four, five or even six times, but all at varying
intervals. The regularity of moulting times, therefore, seems to
be confined to the breeding seasons of the females and the
developmental stages of the young.
The age at which the young woodlice commence to breed
appears to vary somewhat with the species ; P. scaber and
O. asellus do not usually produce brood until they are two
years old, but the smaller forms such as T. pusillus appear to be
capable of breeding earlier—even within twelve months of birth.
It would seem, however, that latitude enters considerably into
determinations of the age at which breeding occurs, the breeding
period of the year, as well as the number of successive broods
which may be produced, since Continental workers record a
much higher fecundity for many of the species.
It is difficult, too, to estimate the average longevity of these
creatures, but roughly it appears to be from three to four years