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Caterpillars exist to perform two duties, eating and avoiding being eaten. The pictures seldom show the caterpillars feeding, but frequently show the defensive structures that keep others from feeding upon them. There are many caterpillars here with hairs or "urticating spines", filled with an irritant that can cause sharp pain. So watch out for the spines, although you never have to worry about a bite; caterpillars never evolved a venomous bite, so you can let even the spined ones walk over you. The wonderful _Acraga hamata_ looks as if it is covered in a mosaic of transparent glass beads; this is gelatinous material that breaks away if the caterpillar is grabbed. Several of the specimens here are hard to see because they look just like a torn leaf or a branch or a mat of fungus. For mimicry, there is nothing to beat _Hemeroplanes triptolemus_, an undistinguished drab green caterpillar when at rest. When disturbed, however, it raises and inflates its hind end, which takes on the appearance of a viper's head, complete with eyes, mouth, and nose spots. It holds still in this position, but if further provoked, can even make the viper's head strike at the offending predator, although there is no threat of a bite. The authors say that even if you know that, it is hard to keep from withdrawing your hand in shock if you are performing the experiment yourself.