Chap. X. SEXUAL SELECTION. 341 



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 Dowers possessed 

 by the males alone — Orthoptera, musical instruments of the 

 males, much diversified in structure; pugnacity; colours — 

 Neuroptera, sexual differences in colour — Hymenoptera, pugnacity 

 and colours — Coleoptera, colours ; furnished with great horns, 

 apparently as an ornament ; battles ; stridulating organs generally 

 common to both sexes. 



In the immense class of insects the sexes sometimes 

 differ in their organs for locomotion, and often in 

 their sense-organs, as in the pectinated and beauti- 

 fully plumose antennae of the males of many species. 

 In one of the Ephemerae, namely Chloeon, the male 

 has great pillared eyes, of which the female is entirely 

 destitute. 1 The ocelli are absent in the females of 

 certain other insects, as in the Mutillida?, which are 

 likewise destitute of wings. But we are chiefly con- 

 cerned 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 contrivances, 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 abdo- 

 men, which ought perhaps to be ranked as primary 



1 Sir J. Lubbock, 'Transact. Linnean Soc.' vol. xxv. 1866. p. 484. 

 With respect to the Mutillidje see Westwood, ' Modern Class, of Insects^' 

 vol. ii. p. 213. 



