COLOR AND COLORATION 



169 



sized imagines. A moderate degree of warmth, however, undoubtedly 

 hastens growth. 



Sexual Coloration. -The sexes are often distinguished by colora- 

 tional as well as structural differences. Colorational antigeny (this 



FIG. 235. Picris protodicc; male (on the left) and female (on the right). Natural size. 



word signifying secondary sexual differences of whatever sort) is most 

 prevalent among butterflies, in which it is the extreme phase of that 

 differentiation of ornamentation for which Lepidoptera are unrivaled. 



The male of Pieris protodice (Fig. 235) has a few brown spots on the 

 front wings; the female is checkered with 

 brown on both wings. In Colias philodice 

 (Fig. 236) and C. eurytheme the marginal 

 black band of the front wings is sharp and 

 uninterrupted in the male, but diffuse and 

 interrupted by yellow spots in the female. 

 In the genus Papilio the sexes are often dis- 

 tinguished by colorational differences and in 

 Hesperiida? the males often have an oblique 

 black dash across the middle of each front 

 wing. Callosamia promethea (Fig. 237), the 

 gypsy moth and many other Lepidoptera 

 exhibit colorational antigeny. In not a few 

 Sesiidae the sexes differ greatly in coloration. 

 Thus in the male of the peach tree borer 

 (Sanninoidea exitiosa) all the wings are color- 

 less and transparent; while in the female the front wings are violet and 

 opaque and the fourth abdominal segment is orange above. The same 

 sex may present two types of coloration, as in males of Cyaniris pseudar- 

 giolus and females of Papilio glaucus, already mentioned. Papilio meropc, 



FIG. 236. Colias pliilodice: 

 right fore wing of male (above) 

 and of female (below). Xat- 

 ural size. 



