274 Tlie Descent of Man. Part II 



to be described in the next chapter, we may feel almost sure that 

 the stridulaticn serves, as Westring also believes, to call or to 

 excite the female ; and this is the first case known to me in the 

 ascending scale of the animal kingdom of sounds emitted for 

 this purpose. 25 



Class, Myriapoda. — In neither of the two orders in this class, 

 the millipedes and centipedes, can I find any well-marked 

 instances of such sexual differences as more particularly concern 

 us. In Glomeris limb da, however, and perhaps in some few 

 other species, the males differ slightly in colour from the females ; 

 but this Glomeris is a highly variable species. In the males of 

 the Diplopoda, the legs belonging either to one of the anterior or 

 of the posterior segments of the body are modified into pre- 

 hensile hooks which serve to secure the female. In some species 

 of lulus the tarsi of the male are furnished with membranous 

 suckers for the same purpose. As we shall see when we treat 

 of Insects, it is a much more unusual circumstance, that it is 

 the female in Lithobius, which is furnished with prehensile 

 appendages at the extremity of her body for holding the male. 26 



CHAPTEE X. 

 Secondary Sexual Characters of Insects. 



Diversified structures possessed bv 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; colours — Neuroptera, sexual differences in colour — Hyme- 

 noptera, 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 locomotive-organs, and often in their sense-organs, as in 

 the pectinated and beautifully plumose antennas of the males of 

 many species. In Chloeon, one of the Ephemeras, the male has 

 great pillared eyes, of which the female is entirely destitute. 1 

 The ocelli are absent in the females of certain insects, as in the 



23 Hilgendorf, however, has lately 'Hist. Nat. des Insectes : Apteres,' 



called attention to an analogous \,^m. iv. 1847, pp. 17, 19, 68. 

 structure in some of the higher ' Sir J. Lubbock, ' Transact. 



crustaceans, which seems adapted Linnean Soc.' vol. xxv. 1866, p. 



te produce sound ; see ' Zoological 484. With respect to the Mu« 



Record,' 1869, p. 603. tillxda see Westwood, « Modern 



26 Walcl.snaer et P. Gervais, Clhss. of Insects,' vol. ii. p. 21.3. 



