THE SKIPPERS
The Hesperiidae or Skipper family includes all the large bodied, small-winged, moth-like butterflies, called Skippers because of their jerky, erratic manner of flight. They are mostly small, dull colored butterflies with short, hooked antennae. The caterpillars are recognized by their large heads and small necks, and usually live in nests made of leaves fastened together with silk. The chrysalids are rounded and moth-like, and (unlike all the other families) are usually enclosed in a loose cocoon of silk. The classification of Skippers is a complicated business; the Hesperiidae is the only family in which the beginner will find it difficult to identify his specimens.
Epargyreus tityrus, the Silver-spotted Skipper, is the largest member of the family, with an expanse of about one and three-fourths inches. The general color is dark brown, with yellowish spots; the common name is derived from the silver area on the lower surface of the hind wing, which shows when the insect is at rest. The caterpillar is yellowish green, with a dark brown head; it feeds upon the leaves of the locust and other leguminous trees. When the caterpillar is mature it leaves its hammock in the locust tree and builds a light silken cocoon upon or near the ground. The Silver-spotted Skipper is found in nearly every part of the United States.
Fig. V.—The Cabbage Butterfly (Pieris rapae). This butterfly was brought over from Europe about 1860, and has spread to every part of the United States and Canada. A, egg; B, caterpillar; C chrysalis; D, imago.
Atalopedes huron, the Sachem Skipper, is a little golden brown species, with an expanse of a little more than an inch. The male has a darker area in the center of the front wing, while in the female the fore wing is marked by several small white spots. When at rest this skipper and its near relatives usually elevate the fore wings and depress the hind wings, an attitude characteristic of this group. The dark, cylindrical caterpillar feeds upon various grasses: the chrysalis is slender, with a little swelling upon the thorax, and the tongue sheath is free as in the pupae of moths. The Sachem is known from New York to Florida, and as far west as eastern Colorado.
Ancyloxipha numitor, the Least Skipper, is the smallest butterfly within our borders, measuring often less than three-fourths of an inch from tip to tip. The slender body and hookless antennae distinguish it from all other skippers. The general color is bright reddish brown, the hind wings being particularly brilliant, and surrounded by a darker border. Its flight is weak and wavering, and it rests often among grasses at the edges of creeks or swamps. The yellow eggs are laid on grasses; the tiny yellow caterpillar has a black head and a body covered with bristles, and lives in a rolled-up blade of grass. The chrysalis is reddish, with small black dots. The Least Skipper is widely distributed everywhere east of the Rocky Mountains.
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.