The important divisions of the body are the thorax and the abdomen. The former is made up of three segments (named the pro-, meso-, and meta-thorax), each of which, as in the caterpillar state, is furnished with a pair of legs; the second and third, which are closely united, each bear a pair of wings also. The legs, which in the butterfly are adapted for walking at a leisurely pace, are made up of four main parts; these are (a) the basal joint (_coxa_, _coxæ_), (_b_) the thigh (_femur_, _femora_), (_c_) the shank (_tibia_, _tibiæ_), and (_d_) the foot (_tarsus_, _tarsi_). The small joint uniting the coxa with the femur is the trochanter (_tr._). The foot usually has five joints, the last of which is provided with claws (_e_). The abdomen really consists of ten rings or segments according to some specialists. Examined from above, the female butterfly appears to have only seven rings and the male butterfly eight. This discrepancy arises from the fact that in the former sex two rings and in the latter one ring are withdrawn into the body, and so are tucked away out of sight. The organs of reproduction are placed in the terminal ring. The breathing arrangements are pretty much as in the caterpillar, but the external openings are not so apparent owing to the dense clothing of the body. [Illustration: FIG. 8. =Leg of Butterfly.=] The beauty of a butterfly's wings is intimately connected with the form and colour of the scales with which they are covered, as with a kind of mosaic; but before the scales and their method of attachment, etc., are referred to, something should be said about the wings themselves. The various shapes of these organs of flight will be seen on turning to the plates, where will be found accurate portraits of every species that will be dealt with in the descriptive section later on. A butterfly's wing consists of an upper and a lower membrane, with a framework of hollow tubes, acting as ribs, between the two layers. Fig. 9, A, shows a fore and a hind wing of the Swallow-tail butterfly. The point of attachment with the thorax is the base of the wing, and the edge farthest from the base is the outer margin (_termen_); the upper edge, or front margin, is the costa; and the lower edge is the inner margin (_dorsum_). The point where the upper margin meets the outer margin on the fore wing is the apex, but on the hind wing it is called the outer angle; the angle formed by the junction of outer and inner margins is the inner angle of the fore wing, but the anal angle of the hind wing. The term _tornus_ is sometimes used for this angle on either wing. Dividing the wings transversely into three portions, we have three areas, termed respectively basal, central or discal, and outer. These are terms used in descriptions of butterflies, and it will be useful to remember them. [Illustration: FIG. 9. =Butterflies' Wings.=]