INSECTS. 311 



CHAPTER X. 



SECONDARY SEXUAL CHARACTERS OF INSECTS. 



Diversified structures possessed by the males for seizing the females 

 Differences between the sexes, of which the meaning is not 

 understood Difference in size between the sexes Thysanura 

 Diptera Hemiptera Homoptera, musical powers possessed 

 by the males alone Orthoptera, musical instruments of the 

 males, much diversified in structure; pugnacity; colors Neu- 

 roptera, sexual differences in color Hymenoptera, pugnacity 

 and colors Coleoptera, colors; furnished with great horns, 

 apparently as an ornament; battles; stridulatiug organs gener- 

 ally common to both sexes. 



IN the immense class of insects the sexes sometimes 

 differ in their locomotive-organs, and often in their sense- 

 organs, as in the pectinated and beautifully plumose anten- 

 nao of the males of many species. In Chloeon, one of tho 

 Ephemerae, the male has great pillared eyes, of which the 

 female is entirely destitute* The ocelli are absent in the 

 females of certain insects, as in theMutillidae; and here the 

 females are likewise wingless. But we are chiefly concerned 

 with structures by which one male is enabled to conquer 

 another, either in battle or courtship, through his strength, 

 pugnacity, ornaments, or music. The innumerable contriv- 

 ances, therefore, by which the male is able to seize the 

 female, may be briefly passed over. Besides the complex 

 structures at the apex of the abdomen, which ought per- 

 haps to be ranked as primary organs, f " i b is ascoiiisumg, as 



*Sir .T. Lubbock, "Transact. Linnean Soc.," vol. xxv, 1866, p. 

 484. With respect to the Mutillidae see Westwood, "Modern Class, 

 of Insects," vol. ii, p. 213. 



f These organs in the male often differ in closely allied species 

 and afford excellent specific characters. But their importance, from 

 a functional point of view, as Mr. R. MacLachlau has remarked to 

 rne, has probably been overrated. It has been suggested that slight 

 differences in these organs would suffice to prevent the intercrossing 

 of well-marked varieties or incipient species, and would thus aid in 



