830 SEXUAL SELECTION. [Part II. 



the female ; and this is the first case in the ascending scale 

 of the animal kingdom, known to me, of sounds emitted 

 for this purpose. 



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

 this class, including the millipedes and centipedes, can I 

 find any well-marked instances of sexual differences such 

 as more particularly concern us. In Glomeris limbata, 

 however, and perhaps in some few other species, the males 

 differ slightly in color from the females ; but this Glomeris 

 is a highly-variable species. In the males of the Diplo- 

 poda, the legs belonging to one of the anterior segments 

 of the body, or to the posterior segment, are modified into 

 prehensile hooks which serve to secure the female. In 

 som*e species of lulus the tarsi of the male are furnished 

 with membranous suckers for the same purpose. It is a 

 much more unusual circumstance, as we shall see when we 

 treat of Insects, that it is the female in Lithobius which is 

 furnished with prehensile appendages at the extremity of 

 the body for holding the male. 17 



17 Walckenaer et P. Gervais, ' Hist. Nat. des Insectes ; Apteres, torn. 

 iv. ISil, pp. 17, 19, 68. 



