ISLAND COMMUNITIES 517 



The decision as to whether an island is to be regarded as conti- 

 nental or as oceanic is not always easy. The British Isles, Japan, the 

 Sunda Islands, are unquestionably continental; Madagascar is prob- 

 ably also a continental island; St. Paul, New Amsterdam, the Cocos 

 Keeling Islands, and the more familiar Azores, Bermudas, and the 

 Hawaiian Islands, are as unquestionably oceanic. The Galapagos 

 Islands are cited by Darwin, Wallace, and many others, as typical 

 oceanic islands, but some recent investigators have referred to them 

 as the last remnants of continental land masses. 2 New Zealand is 

 regarded as continental by Wallace, 3 but some geologists, like Wilkens, 

 regard such connection as improbable. In such disagreements the argu- 

 ment rests heavily on the composition of the insular fauna; but in 

 these ancient islands the differences between the two tj'pes of fauna 

 are much erased; since continental islands may receive transported 

 animals, and their faunal relations may be obscured by extinction, 

 the interpretation of their faunae offers much difficulty. Amphibians 

 are present in the Fiji Islands; they are absent in the presumably 

 continental New Caledonia. In such historic problems, the difficulties 

 increase with increasing geological age, and the two categories of 

 islands are not emphasized in the present chapter, though it is neces- 

 sary to return to them repeatedly in the illustration of the two extreme 

 types of faunal composition. 



The special character of insular faunae rests on the conditions 

 common to all islands — isolation, space restriction, and special insular 

 climates. 



Isolation. — The most important and effective of these factors is 

 that of isolation, which term is in fact derived from "isola" (=islands) . 

 The sea as a barrier makes access to any island impossible to numerous 

 animals. Not all, however, are excluded. Flying animals of all sorts 

 reach islands, favored sometimes by prevailing winds. Animals which 

 can swim well in salt water, such as crocodiles (for example on the 

 Solomon Islands), or snakes, such as the European water snake, may 

 reach islands which are not too distant. Others are transported on 

 driftwood, to which they have attached themselves (snails, for ex- 

 ample), or in which they live as larvae or pupae, or in the earth (as 

 eggs) transported by tree roots. 



Ease of transport explains the predominance on many islands of 

 weevils, whose larvae frequently live in wood. In New Zealand 737 

 species out of 2787 species of beetles are weevils; in the Mariana 

 Islands they predominate; in Madeira there are 80 out of 482 forms; 

 in St. Helena 31 of 60 endemic forms are weevils; in the Falkland 



