AFFINITIES CONNECTING ORGANIC BEINGS 467 



butterfly inhabiting the same district, this variety, from its 

 resemblance to a flourishing and little-persecuted kind, has 

 a better chance of escaping destruction from predaceous 

 birds and insects, and is consequently oftener preserved ;— 

 "the less perfect degrees of resemblance being generation 

 after generation eliminated, and only the others left to pro- 

 pagate their kind." So that we have an excellent illus- 

 tration of natural selection. 



Messrs. Wallace and Trimen have likewise described sev- 

 eral equally striking cases of imitation in the Lepidoptera of 

 the Malay Archipelago and Africa, and with some other in- 

 sects. Mr. Wallace has also detected one such case with 

 birds, but we have none with the larger quadrupeds. The 

 much 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 animals which prey on them; therefore, speaking 

 metaphorically, they are reduced, like most weak creatures, 

 to trickery and dissimulation. 



It should be observed that the process of imitation prob- 

 ably never commenced between forms widely dissimilar in 

 colour. But starting with species already somewhat like 

 each other, the closest resemblance, if beneficial, could read- 

 ily be gained by the above means; and if the imitated form 

 was subsequently and gradually modified through any agency, 

 the imitating form would be led along the same track, and 

 thus be altered to almost any extent, so that it might ulti- 

 mately assume an appearance or colouring 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 nec- 

 essary to suppose in some cases that ancient members belong- 

 ing 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 perfect resemblance. 



On the Nature of the Affinities connecting Organic 



