170 



ENTOMOLOGY 



of South Africa, is remarkable in having three females, which are entirely 

 different in coloration from one another and from the male. There 

 is no longer any doubt, it may be added, as to the specific identity of 

 these forms. 



Next to Lepidoptera, Odonata most frequently show colorational 

 antigeny. The male of Calopteryx maculata is velvety black; the female 



smoky, with a white ptero- 

 stigmatal spot. Among 

 Coleoptera, the male of 

 Hoplia trifasciata is grayish 

 and the female reddish 

 brown; a few more ex- 

 amples might be given, 

 though sexual differences in 

 coloration are comparative- 

 ly rare among beetles. Of 

 Hymenoptera, some of the 

 Tenthredinidae exhibit col- 

 orational antigeny. 



Among tropical butter- 

 flies there are not a few in- 

 stances in which the special 

 coloration of the female is 

 a d a p t i v e harmonizing 

 with the surroundings or 

 else imitating with remark- 

 able precision the colora- 

 tion of another species 

 which is known to be im- 

 mune from the attacks of 

 birds as described beyond. 

 In this way, as Wallace sug- 

 gests, the egg-laden females 



may escape destruction, as they sluggishly seek the proper plants upon 

 which to lay their eggs. Here would be a fair field for the operation of 

 natural selection. 



In most insects, however, sexual differences in coloration are ap- 

 parently of no protective value and are usually so trivial and variable 

 as probably to be of no use for recognition purposes. The usual state- 

 ment that these differences facilitate sexual recognition is a pure as- 



FIG. 237. Callosamia promethca; A , male, clinging to 

 cocoon; B, female. Reduced. 



