2o4 THE OliiaiX OF SPECIES 



some other insects. ]Mr. Wallace has also detected one 

 such case with birds, bat we have none with the larger 

 quadrupeds. The nuich greater frequency of imitation 

 with insects than with other animals is probably the 

 consequence of their small size; insects cannot defend 

 themselves, excepting indeed the kinds furnished with a 

 sting, and I have never heard of an instance of such 

 kinds mocking other insects, though they are mocked; 

 insects cannot easily escape by flight from the larger 

 anirnals which prey oti them ; therefore, speaking meta- 

 phorically, they are reduced, like most weak creatures, 

 to trickery and dissimulation. 



It should be observed that the process of imitation 

 probably never commenced between forms widely dis- 

 similar in color. But starting with species already some- 

 what like each other, the closest resemblance, if bene- 

 ficial, could readily be gained by the above means; and 

 if the imitated form was subsequently and gradually 

 modified through any agencj', the imitating fonn would 

 be led along the same track, and thus be altered to 

 almost any extent, so that it might ultimately assume 

 AH appearance or coloring wholly unlike that of the other 

 members of the family to which it belonged. There is, 

 however, some difficulty on this head, for it is necessary 

 to suppose in some cases that ancient members belonging 

 to several distinct groups, before they had diverged to 

 their present extent, accidentally resembled a member of 

 another and protected group in a sufficient degree to 

 afford some slight protection; this having given the 

 basis for the subsequent acquisition of the most per- 

 fect resemblance. 



