cuticle to furnish a clothing for their own bodies. Among these insects,
while the mouth of the imago is of the normal mandibulate type adapted
for eating solid food, the larval mouth is constricted and the slender
mandibles are grooved for the transmission of liquid food.

Turning to eruciform types of larva, we find the _caterpillar_ (fig. 1
_b_, _c_, _d_) distinguished by its elongate, usually cylindrical body
with feeble cuticle, short thoracic legs and a variable number of pairs
of abdominal pro-legs, universal among the moths and butterflies forming
the great order Lepidoptera, and usual among the saw-flies, which belong
to the Hymenoptera. The vast majority of caterpillars feed on the leaves
of plants and their long worm-like bodies with the series of paired
pro-legs, are excellently adapted for their habit of clinging to twigs,
and crawling along shoots or the edges of leaves as they go in search of
food. Of great importance to a caterpillar is its power of spinning
silk, consisting of fine threads solidified from the secretion of
specially modified salivary glands whose ducts open in the insect's
mouth at the tip of the tubular tongue which forms a spinneret.

On the same bush caterpillars of moths and of saw-flies may often be
seen feeding together. The lepidopterous caterpillar, in our countries
at least, has never more than five pairs of pro-legs, situated on the
third, fourth, fifth, sixth, and tenth abdominal segments; each of these
pro-legs bears a number of minute hooklets, arranged in a circular or
crescentic pattern, which assist the caterpillar in clinging to its
food-plant. The saw-fly caterpillar, on the other hand, may have as many
as eight pairs of pro-legs, the series beginning on the second abdominal
segment; here, however, the pro-legs have no hooklets. Among the
Lepidoptera, we notice a reduction in the number of pro-legs in the
'looper' caterpillars of Geometrid moths. Here only two pairs are