COMMON BUTTERFLIES OF THE PLAINS OF INDIA. 571 



segment or prothorax supports the anterior or front pair of legs. The 

 second, the mesothorax, supports the middle pair of legs and the 

 forewings. The third, or metathorax, the posterior leg? and the 

 hindwings. 



A butterfly's leg consists normally of 5 segments : (1) the coxa, a 

 short joint attached to the thorax ; (2) the trochanter which is a small 

 pivot connecting the coxa with (3) the femur or thigh ; (4) the tibia, 

 which normally carries two pairs of spurs, one pair about the middle 

 and the other at the apex where it joins (5) the tarsus. This is sub- 

 divided into 5 small joints and bears a pair of claws at the apex. The 

 wings are triangular in shape, the upper side being known as the 

 " costa, " the lower as the " dorsum" or inner margin, and the outer 

 as the " termen " or outer margin. 



They are interlaced with a number of nervures or veins whose varia- 

 tions are extremely important. 



For simplicity each vein is known by a number, as will be seen from 

 the figures b3low of the wings of Ismene jaina, which approximates very 

 nearly to the type from which all the variations we shall speak of 

 digress. 



