Chap. XL] SUMMARY ON INSECTS. 407 



^^loration prevails throughout a group, aud we find that 

 the males of some species differ widely in color from the 

 females, while both sexes of other species are quite alike, 

 with intermediate gradations connecting these extreme 

 states. 



In the same manner as bright colors 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 vocal or instru- 

 mental organs proper to the males of the Homoptera and 

 Orthoptera have generally been transferred in a rudimen- 

 tary, or even in a nearly perfect condition to the females ; 

 yet not sufficiently i:)erfect to be used for producing sound. 

 It is also an interesting fact, as bearing on sexual selec- 

 tion, that the stridulating organs of certain male Orthop- 

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

 the colors of certain male dragon-flies are not fully devel- 

 oped until some little time after their emergence from the 

 pupal state, and when they are ready to breed. 



Sexual selection implies that the more attractive indi- 

 viduals are preferred by the opposite sex ; and as with in- 

 sects, when the sexes differ, it is the male whicli, with 

 rare exceptions, is the most ornamented and departs most 

 from the type to wliich the species belongs, and as it is 

 the male which searches eagerly for the female, we must 

 suppose that the females habitually or occasionally prefer 

 the more beautiful males, and that these have thus ac- 

 quired their beauty. That in most or all the orders the 

 females have the power of rejecting any particular male, 

 we may safely infer from the many singular contrivances 

 })0ssessed by the males, such as great jaws, adhesive 

 cushions, spines, elongated legs, etc., for seizing the 

 female ; for these contrivances show that there is some 

 difficulty in the act. In the case of unions between dis- 

 tinct species, of which many instances have been recorded, 



