r
oblique, as on the great caterpillars of most Hawk Moths (Sphingidae).
Such an arrangement tends to make the insect less easily seen than were
it to display a continuous area of the same colour. The 'looper'
caterpillars mentioned above afford remarkable examples of 'protective'
resemblance, for many of them show a marvellous likeness to the twigs of
their food-plant, tubercles on the insect's body resembling closely the
little outgrowths of the plant's cortex. It has been shown by E.B.
Poulton (1892) that many caterpillars are, in their early stages,
directly responsive to their surroundings as regards colour. Usually
green when hatched, they remain green if kept among leaves or young
shoots of plants, while they turn red, brown, or blackish if placed
among twigs of these respective hues. This effect appears to be due to a
direct response of the subcutaneous tissue to the rays of light
reflected from the surrounding objects. The sensitiveness dies away as
the caterpillar grows older, since little or no change of hue in
response to a change of environment could be induced after the
penultimate moult.

[7] The 'hairs' of an insect are not in the least comparable to the
hairs of mammals, being in truth, modified portions of the cuticle,
secreted by special cells.

Among those families of the Lepidoptera which are usually regarded as
low in the scale of organisation, caterpillars are very generally
protected by the habit of feeding in some concealed situation. For
example, the great larvae of the Goat Moth (Cossus) and the whitish
caterpillars of the Clearwing Moths (Sesiidae) burrow through the wood
of trees, eating the timber as they go. The little irritable
caterpillars of the Bell Moths (Tortricidae) roll leaves, fastening the
edges together with silk, and thus make for themselves a shelter; or
they bore their way into seeds or fruits, like the larva of the Codling
Moth that is the cause of 'worm-eaten' apples, too well-known to
orchard-keepers. Very many small caterpillars mine between the two skins
of a leaf, eating out the soft green tissue, and giving rise to a
characteristic blister in form of a spreading patch or a narrow sinuous
track through the leaf. The caterpillars of the Clothes-moths (Tineidae)
make for themselves garments out of their own excrement, the particles
fastened together by silk. In such curious cylindrical cases they wander
over the wool or fur, feeding and indirectly supplying themselves w