216 ISLAND INSECTS. [CH. IV 



and to the elytra of the Coleoptera ; furthermore the 

 plantar surface of the foot including the toes is covered 

 with very soft and very lax integumental tissue deeply 

 wrinkled." These peculiarities of structure, thinks Dr 

 Dobson, must have some relation to the habits of the bat. 

 The probability seems to be that the structure of the feet 

 gives to the animal an unusual power of grasping tightly 

 any rough surface like the bark of a tree, while the wings 

 not being needed when the creature is in such a situation 

 are protected from injury by being carefully stowed away 

 in the fashion described. Dr Dobson is of opinion that 

 this bat instead of hunting its prey on the wing seeks it 

 upon the trunks and branches of trees up and along 

 which the bat crawls. This curious modification of struc- 

 ture therefore is probably an indirect effect of living upon 

 an island where there are but few flying insects. From 

 the same group of animals may be drawn another example 

 of modification of structure having a relation to habitat. 

 In the Bermudas, which are 700 miles from the American 

 coast, are two species of bats ; but one only in the Azores, 

 which are closer to the island of Madeira by about 150 

 miles. The presence of these animals is said to be due 

 to the occasional prevalence of violent storms. It is 

 remarkable that these species have a robuster and more 

 hairy body, which would of course tend to endow them with 

 a greater power of withstanding the violence and coldness 

 of a long-continued gale. 



Another highly remarkable association of structure 

 with locality is afforded by the flightless insects of many 

 oceanic islands. Attention has been already directed to 



