528 The Descent of Man. Part II 



horns, riiagmfied 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 aro 

 brilliantly-coloured, 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-coloured and 

 differs conspicuously from the female, as with some dragon-flies 

 and many butterflies, it is probable 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. But in some cases the female has apparently 

 been made obscure by variations transmitted to her alone, 

 as a means of direct protection ; and it is almost certain that 

 she has sometimes been made brilliant, so as to imitate other 

 protected species inhabiting the same district. When the sexes 

 resemble each other and both are obscurely coloured, there is 

 no doubt that they have been in a multitude of cases so coloured 

 for the sake of protection. So it is in some instances when both 

 are brightly-coloured, for they thus imitate protected species, or 

 resemble surrounding objects such as flowers; or they give 

 notice to their enemies that they are unpalatable. In other 

 cases in which the sexes resemble each other and are both 

 brilliant, especially when the colours are arranged for display, 

 we may conclude that they have been gained by the male sex as 

 an attraction, and have been transferred to the female. We are 

 more especially led to this conclusion whenever the same type 

 of coloration prevails throughout a whole group, and we find 

 that the males of some species differ widely in colour from 

 the females, whilst others differ slightly or not at all, with 

 intermediate gradations connecting these extreme states. 



In the same manner as bright colours have often been 

 partially transferred from the males to the females, so it has 

 been with the extraordinary horns of many Lamellicorn and 

 some other beetles. So again, the sound-producing organs 

 proper to the males of the Homoptera and Orthoptera have 

 generally been transferred in a rudimentary, or even in a nearly 

 perfect condition, to the females; yet not sufficiently perfect to 

 be of any use. It is also an interesting fact, as bearing on 

 sexual selection, that the stridulating organs of certain male 

 Orthoptera are not fully developed until the last moult; and that 

 the colours of certain male dragon-flies are not f ally developed 

 antil some little time after their emergence from the pupa] 

 state, and when they are ready to breed. 



