SEXUAL SELECTION 427 



these musical instruments have been acquired through sex- 

 ual selection. In four other Orders the members of one 

 sex, or more commonly of both sexes, are provided with 

 organs for producing various sounds, which apparently 

 serve merely as call-notes. When both sexes are thus 

 provided, the individuals which were able to make the 

 loudest or most continuous noise would gain partners be- 

 fore those which were less noisy, so that their organs have 

 probably been gained through sexual selection. It is in- 

 structive to reflect on the wonderful diversity of the means 

 for producing sound, possessed by the males alone, or by 

 both sexes, in no less than six Orders. We thus learn how 

 effectual sexual selection has been in leading to modifica- 

 tions which sometimes, as with the Homoptera, relate to 

 important parts of the organization. 



Prom the reasons assigned in the last chapter, it is prob- 

 able that the great horns possessed by the males of many 

 Lamellicorn, and some other beetles, have been acquired as 

 ornaments. From the small size of insects, we are apt to 

 undervalue their appearance. If we could imagine a male 

 Chalcosoma (Fig. 16), with its polished bronzed coat of mail, 

 and its vast complex horns, magnified to the size of a horse, 

 or even of a dog, it would be one of the most imposing 

 animals in the world. 



The coloring of insects is a complex and obscure subject. 

 When the male differs slightly from the female, and neither 

 is brilliantly colored, it is probable that the sexes have 

 varied in a slightly different manner, and that the variations 

 have been transmitted by each sex to the same, without any 

 benefit or evil thus accruing. When the male is brilliantly 

 colored and differs conspicuously from the female, as with 

 gome dragon-flies and many butterflies, it is probable that 

 he owes his colors to sexual selection; while the female 

 has retained a primordial or very ancient type of coloring, 

 slightly modified by the age acies before explained. But in 

 Bome cases the female has apparently been made obscure 

 by variations transmitted to her alone, as a means of direct 



