288 



Natural History 



pigeons. A short and rounded wing, on the other hand, al- 

 ways accompanies a more feeble or more laborious flight, and 

 one much less under command. We might suppose, there- 

 fore, that the butterflies which possess this peculiar form were 

 better able to escape pursuit. But there seems no unusual 

 abundance of insectivorous birds to render this necessary ; and 



as we can not believe that such a curious peculiarity is without 

 meaning, it seems probable that it is the result of a former 

 condition of things, when the island possessed a much richer 

 fauna, the relics of which we see in the isolated birds and Mam- 

 malia now inhabiting it ; and when the abundance of insectiv- 

 orous creatures rendered some unusual means of escape a ne- 



