24G 



ISLAND LIFE. 



[part II. 



become extinct in their native country ; and in the second place, 

 insects have many more chances of reaching remote islands than 

 birds, for not only may they be carried by gales of wind, but 

 sometimes, in the egg or larva state or even as perfect insects, 

 they may be drifted safely for weeks over the ocean, buried in 

 the light stems of plants or in the solid wood of trees in which 

 many of them undergo their transformations. Thus we may 

 explain the presence of three common South American species 

 (two elaters and a longicorn), all wood-eaters, and therefore 

 liable to be occasionally brought in floating timber by the Gulf 

 Stream. But insects are also immensely more numerous in 

 species than are land-birds, and their transmission would be in 

 most cases quite involuntary, and not dependent on their own 

 powers of flight as with birds ; and thus the chances against the 

 same species being frequently carried to the same island would 

 be considerable. If we add to this the dependence of so many 

 insects on local conditions of climate and vegetation, and their 

 liability to be destroyed by insectivorous birds, we shall see that, 

 although there may be a greater probability of insects as a whole 

 reaching the islands, the chance against any particular insect 

 arriving there, or against the same species arriving frequently, 

 is much greater than in the case of birds. The result is, that 

 (as compared with Britain for example) the birds are, pro- 

 portionately, much more numerous than the beetles, while the 

 peculiar species of beetles are much more numerous than among 

 birds, both facts being quite in accordance with what we know 

 of the habits of the two groups. We may also remark, that the 

 small size and obscure characters of many of the beetles renders 

 it probable that species now supposed to be peculiar, really 

 inhabit some parts of Europe or North Africa. 



It is interesting to note that the two families which are pre- 

 eminently wood, root, or seed eaters, are those which present the 

 greatest amount of speciality. The two Elateridse alone exhibit 

 remote affinities, the one with a Brazilian the other with a 

 Madagascar group ; while the only peculiar genera belong to the 

 Ehyncophora, but are allied to European forms. These last 

 almost certainly form a portion of the more ancient fauna of the 

 islands which migrated to them in pre-giaciar times, while the 



