158 TRANSITIONS 01 ORGANIC BEINGS. 



I will now give two or three instances, both of diversified 

 and of changed habits, in the individuals of the same species. 

 In either case it would be easy for natural selection to adapt 

 the structure of the animal to its changed habits, or exclu- 

 sively to one of its several habits. It is, however, difficult to 

 decide and immaterial for us, whether habits generally 

 change first and structure afterward ; or whether slight mod- 

 ifications of structure lead to changed habits ; both probably 

 often occurring almost simultaneously. Of cases of changed 

 habits it will suffice merely to allude to that of the many 

 British insects which now feed on exotic plants, or exclu- 

 sively on artificial substances. Of diversified habits innu- 

 merable instances could be given : I have often watched a 

 tyrant flycatcher (Saurophagus sulphuratus) in South Amer- 

 ica, hovering over one spot and then proceeding to another, 

 like a kestrel, and at other times standing stationary on the 

 margin of water, and then dashing into it like a kingfisher 

 at a fish. In our own country the larger titmouse (Parus 

 major) may be seen climbing branches, almost like a creeper ; 

 it sometimes, like a shrike, kills small birds by blows on the 

 head ; and I have many times seen and heard it hammering 

 the seeds of the yew on a branch, and thus breaking them 

 like a nuthatch. In North America the black bear was seen 

 by Hearne swimming for hours with widely open mouth, thus 

 catching, almost like a whale, insects in the water. 



As we sometimes see individuals following habits differ- 

 ent from those proper to their species and to the other 

 species of the same genus, we might expect that such indi- 

 viduals would occasionally give rise to new species, having 

 anomalous habits, and with their structure either slightly or 

 considerably modified from that of their type. And such 

 instances occur in nature. Can a more striking instance of 

 adaptation be given than that of a woodpecker for climbing 

 trees and seizing insects in the chinks of the bark ? Yet in 

 North America there are woodpeckers which feed largely on 

 fruit, and others with elongated wings which chase insects 

 on the wing. On the plains of La Plata, where hardly a 

 tree grows, there is a woodpecker (Colaptes campestris) 

 which has two toes before and two behind, a long-pointed 

 tongue, pointed tail-feathers, sufficiently stiff to support the 

 bird in a vertical position on a post, but not so stiff as in the 

 typical woodpeckers, and a straight, strong beak. The beak, 

 however, is not so straight or so strong as in the typical 

 woodpeckers, but it is strong enough to bore into wood. 



