248 ANIMAL COLORATION. 



to protected forms, it follows as a matter of course that the 

 males do not. Hence a gradual dwindling of the male insect 

 must take place, which, if it does not result in extinction, must 

 materially interfere with the chances of a given female securing 

 a mate ; thus, in any case there would be a diminution in the 

 number of the species. This difficulty is partly met by Mr. 

 Wallace's suggestion that the females need an additional 

 protection because their flight is slower, owing to their being 

 laden with eggs, and they are exposed to attack when actually 

 depositing their eggs. Presumably, therefore, at other times 

 they are as well able to take care of themselves as the males. 

 But this suggestion does not altogether remove the difficulty : 

 it has to be definitely proved that a butterfly with eggs is 

 markedly slower in its flight than one without ; as to the 

 exposure to enemies while actually depositing the eggs, this, 

 no doubt, constitutes a real danger ; but the time so occupied 

 is not long, and it might be urged that the pairing was equally 

 dangerous ; and the danger incurred here is shared by both 

 sexes alike. 



Mr. Belt has made an additional suggestion, which, although 

 very ingenious, no doubt needs confirmation, as Mr. Poulton 

 says, by a careful observation of the habits displayed during 

 courtship. 



The suggestion is that the females exert a selective influence 

 upon the males, not in the direction in which sexual selection 

 is generally supposed to proceed (see p. 2(53): instead of prefer- 

 ring the more brilliantly coloured males they are believed by 

 Mr. Belt to exhibit " a deep-seated preference for the normal 

 colour of the order to which these mimetic forms belong." 

 This explanation does not satisfy Dr. Scudder, in spite of his 

 opinion that the female butterfly if the two sexes differ is 

 farther from the normal coloration than the male. If the con- 



