Chap. XI. SUMMARY OX INSECTS. 419 
through, sexual selection. It is instructive 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, 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 some- 
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