Page:Darwinism by Alfred Wallace 1889.djvu/225

Rh leaf-insects of Ceylon and of Java, species of Phyllium, are so wonderfully coloured and veined, with leafy expansions on the legs and thorax, that not one person in ten can see them when resting on the food-plant close beneath their eyes. Others resemble pieces of stick with all the minutiæ of knots and branches, formed by the insects' legs, which are stuck out rigidly and unsymmetrically. I have often been unable to distinguish between one of these insects and a real piece of stick, till I satisfied myself by touching it and found it to be alive. One species, which was brought me in Borneo, was covered with delicate semitransparent green foliations, exactly resembling the hepaticæ which cover pieces of rotten stick in the damp forests. Others resemble dead leaves in all their varieties of colour and form; and to show how perfect is the protection obtained and how important it is to the possessors of it, the following incident, observed by Mr. Belt in Nicaragua, is most instructive. Describing the armies of foraging ants in the forest which devour every insect they can catch, he says: "I was much surprised with the behaviour of a green leaf-like locust. This insect stood immovably among a host of ants, many of which ran over its legs without ever discovering there was food within their reach. So fixed was its instinctive knowledge that its safety depended on its immovability, that it allowed me to pick it up and replace it among the ants without making a single effort to escape. This species closely resembles a green leaf."

Caterpillars also exhibit a considerable amount of detailed resemblance to the plants on which they live. Grass-feeders are striped longitudinally, while those on ordinary leaves are always striped obliquely. Some very beautiful protective resemblances are shown among the caterpillars figured in Smith and Abbott's Lepidopterous Insects of Georgia, a work published in the early part of the century, before any theories of protection were started. The plates in this work are most beautifully executed from drawings made by Mr. Abbott, representing the insects, in every case, on the plants which they frequented, and no reference is made in the descriptions to the remarkable protective details which appear upon the plates. We have, first, the larva of Sphinx fuciformis feeding