msECTS, 311 



CHAPTER X. 



SECONDARY SEXUAL CHARACTERS OF IKSECTS. 



Diversified structures possessed by the males for seizLo^ 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; stridulating organs gener- 

 ally common to both sexes. 



lis 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- 

 nae of the males of many species. In Chloeon, one of the 

 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 the Mutillidae; 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 be ranked as primary organs, f '* it is astonishing," as 



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

 484. With respect to the Mutillidae see VVestwood, " Modem Class, 

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



f These organs in the male often differ in closely allied sx)ecies 

 and afford excellent si)ecific characters. But their importance, from 

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

 me, has probably been overrated. It ha.s been suggested that slight 

 differences in thc^se organs would suffice to prevent the intercrossing 

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



