20 OLD-WORLD MIMICS [ch. 



may be subdivided into five main groups or families ^ 

 according to the structure of the first of their three 

 pairs of legs. In the Papilionidae or "swallow-tails," 

 the first pair of legs is well developed in both sexes 

 (Pig. 8). In the Pieridae or "whites," the front legs 

 are also similar in both sexes, but the claws are bifid 

 and a median process, the empodium, is found between 

 them (Fig. 7). In the remaining three families the 

 front legs difier in the two sexes. The females of the 

 Lyeaenidae or "blues" have well-developed front legs 

 in which the tarsus is terminated by definite claws 

 (Fig. 5), whereas in the males the terminal part of the 

 leg, or tarsus, is un jointed and furnished with but a 

 single small claw (Fig. 6). This reduction of the 

 front legs has gone somewhat further in the Erycinidae 

 (Figs. 3 and 4), a family consisting for the most part 

 of rather small butterflies and specially characteristic 

 of South America. In the great family of the Nym- 

 phalidae the reduction of the front legs is well marked 

 in both sexes. Not only are they much smaller than 

 in the other groups, but claws are lacking in the female 

 as well as in the male (Figs. 1 and 2). 



Though the structure of the fore limbs is the 

 character specially chosen for separating these different 

 families from one another, it is of course understood 

 that they differ from one another in various other 

 distinctive features. The chrysalis of the Nymphahdae 

 for example hangs head downwards suspended by the 



^ Oimtting the Hesperidae which hardly enter into questions of 

 mimicry. 



