78 NATURAL SELECTION in 



same district, whereas allied forms of every degree of nearness 

 and remoteness generally inhabit different countries, and 

 often different quarters of the globe ; and neither it nor 

 "similar conditions" will account for the likeness between 

 species of distinct groups being superficial only a disguise, 

 not a true resemblance ; for the imitation of bark, of leaves, 

 of sticks, of dung ; for the resemblance between species in 

 different orders, and even different classes and sub-kingdoms ; 

 and finally, for the graduated series of the phenomena, 

 beginning with a general harmony and adaptation of tint in 

 autumn and winter moths and in arctic and desert animals, 

 and ending with those complete cases of detailed mimicry 

 which not only deceive predacious animals, but puzzle the 

 most experienced insect collectors and the most learned 

 entomologists. 



Mimicry by Female Insects only 



But there is yet another series of phenomena connected 

 with this subject, which considerably strengthens the view 

 here adopted, while it seems quite incompatible with either 

 of the other hypotheses; namely, the relation of protective 

 colouring and mimicry to the sexual differences of animals. 

 It will be clear to every one that if two animals, which as 

 regards " external conditions " and " hereditary descent " are 

 exactly alike, yet differ remarkably in coloration, one 

 resembling a protected species and the other not, the resem- 

 blance that exists in one only can hardly be imputed to the 

 influence of external conditions or as the effect of heredity. 

 And if, further, it can be proved that the one requires 

 protection more than the other, and that in several cases it is 

 that one which mimics the protected species, while the one 

 that least requires protection never does so, it will afford 

 very strong corroborative evidence that there is a real con- 

 nection between the necessity for protection and the pheno- 

 menon of mimicry. Now the sexes of insects offer us a test 

 of the nature here indicated, and appear to furnish one of 

 the most conclusive arguments in favour of the theory that 

 the phenomena termed " mimicry " are produced by natural 

 selection. 



The comparative importance of the sexes varies much in 



