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. VARIETIES 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_. CHAPTER VI THE FOUR FAMILIES As we said in the chapter on Classification, American butterflies fall naturally into four great groups called families: the _Nymphalidae_ or Four-footed family, the _Lycaenidae_ or Gossamer-winged family, the _Papilionidae_ or Swallowtail family, and the _Hesperiidae_ or Skipper family. THE FOUR-FOOTED BUTTERFLIES The largest family of butterflies in America is the _Nymphalidae_, and its members are called four-footed butterflies because the front legs are so small as to be useless, leaving only four walking feet. Most of the butterflies are large or medium-sized, the caterpillars are usually provided with spines or fleshy protuberances, and the chrysalids are always suspended by the tail. The family is divided into five subfamilies; the _Euploeinae_, the _Heliconiinae_, the _Nymphalinae_, the _Satyrinae_, and the _Libytheinae_. THE EUPLOEINAE [Illustration: Fig. III.--The Silver-Spotted Skipper (_Epargyreus tityrus_), a typical Hesperid. A, egg; B, mature caterpillar; C, pupa or chrysalis; D, imago.]