CHAPTER VII ENEMIES AND PROTECTION Butterflies have many enemies. Even the eggs of butterflies are often discovered by tiny, four-winged parasites, which pierce the egg-shell and deposit their own microscopic eggs inside. These eggs produce little grubs, which devour the contents of the butterfly’s egg, so that the latter develops into a caterpillar. The chief enemies of the butterfly tribe, however, are the insectivorous birds, whose summer food often consists largely of caterpillars. Caterpillars are also attacked by wasp-like parasites which deposit their eggs in the victim’s skin; when the eggs hatch the parasitic grubs feed upon the flesh of their unwilling host, who usually dies about the time the guests are ready to pupate. One often sees dead or dying caterpillars covered with the white cocoons of these hymenopterous parasites. Certain larger wasps, too, use caterpillars as food for their young. These insects paralyze their prey by stinging it, lay their eggs on the helpless body, and seal it up in a hollow reed, or in a nest of mud. When the wasp larva hatches it finds plenty of living food at hand. Chrysalids also are eaten by birds and by various carnivorous insects, and are frequently killed by parasitic wasps and flies. Many an amateur butterfly-hunter has been puzzled to see that some of his chrysalids produce, not beautiful butterflies, but a lot of insignificant little wasps. Adult butterflies are not much troubled by parasitic insects, but they are eaten by many birds, particularly those of the fly-catcher type, by lizards, and by the larger dragonflies. Spiders kill a few, the great gray robber-flies carry off a butterfly now and then, and frogs and toads take them whenever possible. They are not much attacked by the mammals, but I have seen a chipmunk devour a large _Papilio turnus_ with every symptom of satisfaction. Long ages of struggle with these enemies have developed certain protective devices--not through any supernatural intervention or any conscious activity on the part of the butterflies, but simply by the mechanical process called natural selection. There is a certain degree of variation among all animals, and some of these variations are transmitted to succeeding generations. Now, if certain butterflies happen to vary in such a way that they are protected against their enemies, they survive at the expense of their less fortunate fellows, and such of their offspring as inherit the protective variation also survive, until at last, by a gradual process of elimination, the entire species is protected. PROTECTIVE COLORATION