The walking leaves (Phyllium) (Fig. 194) are clever mimics, resembling leaves. Even the veins and midrib of the leaf are imitated, and the insect, when crouching on a limb, is a virtual leaf, so far as appearance goes, the disguise being absolutely perfect. Some resemble green leaves; others dried and withered specimens. Even the legs of these insects are supplied with a singular growth. Most of these strange mimics are found clinging to trees; but one common in Brazil spends most of the time during the day under water in streams, where it clings to the pebbles. In Nicaragua there are several species that resemble leaves in all stages of decay. The movements of some of these insects resemble those of leaves. I saw one in the Sierra Madre range come down from a tall sycamore, and supposed it a leaf, as it dropped slowly, zigzagging down. I should not have discovered the mistake had not my dog recognized it.
Fig. 194.—Walking leaf.
XXIII. THE GRASSHOPPERS AND LOCUSTS
These forms may be considered the musicians of the insect world. None of the insects can produce vocal sounds, that is, they have no voice, but they have certain appliances which enable them to produce sounds which can be heard a long distance. On hot days in summer is heard the constant and shrill zee-zeeing of the locust, while countless varieties lend their aid in producing a volume of sound.
Fig. 195.—A grasshopper.
The "instruments" in the locust are (Fig. 196) minute teeth, arranged along the thighs; these are rubbed against the fore wings, producing the remarkable sounds. The locusts are commonly called grasshoppers. They have two pairs of net-veined wings, and hind legs adapted for leaping, by which they send themselves sprawling through the air, almost invariably using this method of escape instead of unfolding their delicate wings. All are mimics. The common ground locust resembles the dusty road and the dried foliage which it affects. Others, which live on plants, are a vivid green. Some which I find in my garden resemble closely the tender shoots of the passion vine, upon which they feed.