_Sex._--The designation of the sex is important in the case of all well-ordered collections of zoölogical specimens. As a measure of convenience, the male is usually indicated by the sign of Mars, ♂, while the female is indicated by the sign of Venus, ♀. The inscription, "_Argynnis Diana_, ♂," therefore means that the specimen is a male of _Argynnis Diana_, and the inscription, "_Argynnis Diana_, ♀," means that the specimen is a female of the same species. These signs are invariably employed by naturalists to mark the sexes. _The Division of Butterflies into Families._--Without attempting to go deeply into questions of classification at the present point, it will be well for us to note the subdivisions which have been made into the larger groups, known as families, and to show how butterflies belonging to one or the other of these may be distinguished from one another. There are five of these families represented within the territory of which this book takes notice. These five families are the following: 1. The NYMPHALIDÆ, or "Brush-footed Butterflies." 2. The LEMONIIDÆ, or "Metal-marks." 3. The LYCÆNIDÆ, or "Blues," "Coppers," and "Hair-streaks". 4. The PAPILIONIDÆ, or the "Swallowtails" and their allies. 5. The HESPERIIDÆ, or the "Skippers." The NYMPHALIDÆ, the "Brush-footed Butterflies." The butterflies of this family may be distinguished as a great class from all other butterflies by the fact that in _both sexes the first, or prothoracic, pair of legs is greatly dwarfed, useless for walking, and therefore carried folded up against the breast_. From this peculiarity they have also been called the "Four-footed Butterflies." This is the largest of all the families of the butterflies, and has been subdivided into many subfamilies. Some of the genera are composed of small species, but most of the genera are made up of medium-sized or large species. The family is geologically very ancient, and most of the fossil butterflies which have been discovered belong to it. The caterpillars are in most of the subfamilies provided with horny or fleshy projections. The chrysalids always hang suspended by the tail. The LEMONIIDÆ, the "Metal-marks."