28 THE BUTTERFLIES OF THE 



the middle, each of which is composed of a great num- 

 ber of rings, convex on the outer part and concave 

 on the inner, and the tube is formed by the union of 

 these concave surfaces. The head is clothed with a dense 

 coat of hair-like scales, often spoken of as hairs, and 

 the arrangement of some of these is of value in deter- 

 mining genera or species. 



The thorax is connected or joined to the .head by the 

 neck, and bears the legs and wings. It consists of three 

 joints, to each of which is attached on the under side a 

 pair of legs, but only the two posterior joints are fur- 

 nished each with a pair of wings. Each leg is composed 

 of a basal joint, called the coxa, at the end of which is a 

 small piece called the trochanter. Beyond this is the femur, 

 the longest joint of the leg ; attached to this is the tibia, 

 followed by the tarsi, or foot, which consists of five joints 

 placed end to end, the last of which usually has a pair 

 of curved claws. The middle and hind tibiae usually 

 have a pair of spurs at the end of each, and are some- 

 times more or less armed with spines. The hind tibia? 

 in some species have an additional pair of spurs near the 

 middle. In some species the front tibiae have an ap- 

 pendage on the middle of each, called an epiphysis. 



In one family, the Nymphalidae, the front legs are so 

 much aborted as to be of no service in walking ; and such 

 are said to be four-footed butterflies. In the other fam- 

 ilies the pair of fore legs is directed forward, and the 

 middle and hind legs backward ; but in this family the 

 second pair of legs is directed forward. 



The first ring of the thorax, the prothoracic, is smaller 

 than the others, and its only appendages are a series of 

 scales arising from the upper side, forming the collar. 



