CHAPTER V
THE CLASSIFICATION OF BUTTERFLIES
In every science it is necessary to manipulate a large number of related facts, and this cannot be done unless the data are arranged in some systematic and orderly fashion. In order to make use of the facts about butterflies, one must know something of the relation of one butterfly to another, and the relation of butterflies in general to the rest of the animal kingdom.
SUBKINGDOMS, CLASSES, ORDERS, AND SUBORDERS
Members of the animal kingdom which have no spinal column, but only an external skeleton composed of horny rings, are assigned to the subkingdom Arthropoda. Arthropods which have six legs are grouped together in the class Insecta. Insects with scales on their wings are assigned to the order called Lepidoptera. This order is divided into two suborders, the Rhopalocera or butterflies and the Heterocera or moths. Butterflies fly in the daytime, and have slender antennae with club-like knobs at the ends; moths are usually nocturnal or crepuscular, and their antennae are not knobbed, but are thread-like, feather-like, or hooked at the extremity.
The suborder Rhopalocera is divided into four families: the Nymphalidae, the Lycaenidae, the Papilionidae, and the Hesperiidae.
The Nymphalidae or four-footed butterflies make up the largest family; the first pair of legs are much smaller than the others, and are quite useless for walking. Most of the Nymphalidae are large or medium-sized butterflies. The caterpillars are usually provided with spines or fleshy protuberances, and the chrysalids are always suspended by the tail.
The Lycaenidae or gossamer-wings are the bright little butterflies known as “blues,” “hair-streaks,” and “coppers.” The males do not use the first pair of legs in walking, but the females do. The caterpillars are small and usually slug-shaped, and the chrysalids are held closely attached to some object by a girdle of silk.
The Papilionidae is the family of the swallowtails and allied forms. Both sexes use all six feet in walking. The butterflies are usually large or medium-sized; many of the caterpillars produce disagreeable odors; the chrysalids are suspended by the tail and provided with a girdle of silk, but not drawn up to the surface to which they are attached, as in the case of the Lycaenidae.
The Hesperids or skippers are small butterflies with thick, moth-like bodies and a peculiar manner of flight. Both sexes have six walking feet. The caterpillars are smooth and thin-necked, with large globular heads. The chrysalids are usually enclosed in a flimsy cocoon of leaves fastened together with a few silk threads.
SUBFAMILIES, GENERA, AND SPECIES
Each one of these four families is divided into several subfamilies; each subfamily is divided into several genera, and each genus is divided into several species, all of these divisions being based on an increasing anatomical similarity. Thus the common Milkweed Butterfly belongs to the class Insecta, the order Lepidoptera, the suborder Rhopalocera, the family Nymphalidae, the subfamily Euploeinae, the genus Anosia, and the species Plexippus.
THE VALUE OF SCIENTIFIC NOMENCLATURE
One may well ask why we do not simply say “milkweed butterfly” and have done with it, but this term refers merely to the fact that the caterpillar feeds upon a certain plant, while Anosia plexippus places the specimen definitely in the scientific scheme of things, and designates important structural distinctions which have nothing to do with milkweeds. The average American is prone to call any insect a “bug” or “moth-miller” or some such unenlightening name, so that many butterflies have no common English name at all, while others have many different names which vary widely in different parts of the country. Besides, the Greek and Latin names are understood by scientists in all countries, and are less liable to corruption than terms taken from the modern languages.
There are difficulties enough in the scientific nomenclature, without complicating matters by the introduction of popular names. It is a fixed rule in science that the first man to discover and describe a species has the right to name it, and that whatever name he chooses shall be used by everybody forever, but scientists are only human after all, and are always anxious to discover new species and name them after their friends or sweethearts. It often happens that a single species is described independently by several authors, each of which applies a name of his own devising; in this case the first is the real name, and the others are called synonyms.
In writing about butterflies it is not customary to spell out the generic name; one does not write Dione vanillae, but merely D. vanillae. It is usual also to add the name of the man who first named the species, so that the name becomes D. vanillae, Linnaeus, or D. vanillae, Linn. In conversation one may omit the name of the genus altogether, and refer to the butterfly simply as Vanillae. It is well to remember that scientific Latin in this country is pronounced in the insular fashion—that is, the words are pronounced as if they were English.
Sometimes the individuals of a species differ in different parts of the country; these different forms are called varieties, and are designated by a varietal name added to the generic and specific names. Papilio turnus, Linn. is a large yellow swallowtail, but in the southern part of its range some of the females are black. The black female was formerly regarded as a distinct species, and Linnaeus named it Papilio glaucus, but when it was reared from eggs laid by a yellow female it was recognized as a variety, and is now known as Papilio turnus, Linn., var. glaucus.