HABITS AND LIFE-HISTORIES OF WOODLICE. 139
to a diet consisting exclusively of fresh carrot, and this proved
to be sufficient for the complete rearing of these creatures
several families being reared from birth for upwards of two years
on this exclusive diet. Other substances, such as potatoes,
mushrooms, bark of trees and leaf mould were tried, but none
proved so universally favourable as carrot. A. vulgare is the
one species which proved an exception to the all-sufficiency of
such a diet, chalk being required in this case in addition. This
is not to be wondered at, since A. vulgare has the most thickly
calcified integument. It was found, in fact, that A. vulgare
will live and breed for quite a considerable time on lumps of
chalk alone, one specimen being kept for two months entirely
on chalk, which it ate readily, though most of it appeared to
pass through the body unchanged. It is, of course, probable
that some calcium supply is necessary for all the species, since
all have the integument calcified to a greater or lesser degree.
The bark of trees, particularly beech trees, is rich in calcium,
and carrot itself contains 0.102% of calcium, which is probably
sufficient for the majority of the species.
It was curious to note also that some of the captive specimens
—particularly P. dilatatus and A. vulgare—added portions of
the blotting paper discs to their diet, and in one case, where
several specimens of P. dilatatus were put together in one dish,
at the end of two months almost the whole of the blotting paper
had been eaten away and left in the faeces—the tissues appearing
little changed as a result of passing through the body.
This observation, coupled with that relating to the eating
of quantities of chalk by A. vulgare, seems to point to the con-
clusion that the paper and the chalk may not all be used as
food, but may provide some sort of "roughage" or "grit" in
the diet, since it appears to pass through almost unchanged. I
have, moreover, been unable to trace the presence of any form of
intestinal Protozoa in these creatures which might be capable of
breaking down cellulose, or the presence of cellulose in the
digestive fluids, both of which are sometimes found in the guts
of insects which feed on the foliage and woody tissues of plants
(Wigglesworth, 1934).
In the same way the surprisingly large quantities of wood
eaten by P. scaber and of decayed leaves eaten by T. pusillus
B