Chap. XI. SUMMAKY ON INSECTS: 419 



through sexual selection. It is instrutive to reflect 

 on the wonderful diversity of the means for producing 

 sound, possessed by the males aloue or by both sexes 

 in no less than six Orders, and which were possessed 

 by at least one insect at an extremely remote geolo- 

 gical epoch. We thus learn how effectual sexual selec- 

 tion has been in leading to modifications of structure, 

 which sometimes, as with the Homoptera, are of an im- 

 portant nature. 



From the reasons assigned in the last chapter, it is 

 probable that the great horns of the males of many 

 lamellicorn, and some other beetles, have been ac- 

 quired as ornaments. So perhaps it may be with cer- 

 tain other peculiarities confined to the male sex. From 

 the small size of insects, we are apt to undervalue their 

 appearance. If we could imagine a male Chalcosoma 

 (fig. 15) with its polished, bronzed coat of mail, and 

 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 colouring of insects is a complex and obscure 

 subject. When the male differs slightly from the female, 

 and neither are brilliantly coloured, it is probable that 

 the two sexes have varied in a slightly different manner, 

 with the variations transmitted to the same sex, without 

 any benefit having been thus derived or evil suffered. 

 When the male is brilliantly coloured and differs con- 

 spicuously from the female, as with some dragon-flies 

 and many butterflies, it is probable that he alone has 

 been modified, and that he owes his colours to sexual 

 selection ; whilst the female has retained a primordial 

 or very ancient type of colouring, slightly modified by 

 the agencies before explained, and has therefore not 

 been rendered obscure, at least in most cases, for the 

 sake of protection. But the female alone has soine- 



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