DERIVATION OF THE FLORA AND FAUNA 347 



time. This does not accord with Zimmerman's statement that no primitive family 

 is represented in Hawaii. Probably the Hawaiian Diptera have been less collected; 

 Zimmerman, who is responsible for the figures quoted, indicates about 400 species, 

 of which 60 % are endemic. In relation to their small size the Juan Fernandez 

 Islands seem to be richer with about i 50 indigenous species (64 % endemic). Our 

 knowledge of the dipterous fauna is in the main due to Dr. KuscilEl/s collec- 

 tions; the 25—30 species not yet reported on will raise the total number. 



Over 1600 species of Colcopiera are reported from Hawaii, of which about 

 'j^ % are endemic, and there are numerous endemic genera. Numerous species 

 found elsewhere are adventitious. In relation to its size, Juan Fernandez cannot 

 be called poor (see above p. 307, etc.), and endemism is just as high here. I presume 

 that Zimmerman and others regard wind as the principal dispersal agent, though 

 not for all kinds of beetles, because we have to do with many different types 

 of animals and of habits and habitats. It is difficult to imagine how a flightless 

 beetle would be able to keep afloat in the air for thousands of miles; he must 

 have had a great need of the numerous "stepping stones" postulated by ZIMMER- 

 MAN. It should perhaps be mentioned that GULICK (77^.414) wrote that "it can 

 hardly be doubted that some carrion-feeding insects have been distributed by 

 adhering to sea birds". I doubt that this ever happened, but as he had just dis- 

 cussed the transport of "invertebrate eggs" in the digestive tract of birds, I sup- 

 pose that he means eggs of necrophilous flies or beetles which, brought across 

 the sea, were deposited on another carrion and thus became established on an 

 oceanic island. 



The taeevils, a most important and interesting feature in isolated island 

 faunas, are often dependent on definite host plants, and are thought to sail along 

 on logs as stowaways. Evidently the Curculionidae have become something of a 

 stumbling-block. UsiNGER (2yj) came to the conclusion that they must possess 

 some unknown special means of dispersal. Brinck, who discussed the coleopterous 

 fauna of Tristan da Cunha (316. 97—104), another isolated volcanic group of islands 

 where geologists failed to discover any traces of land connections, states that 

 the fauna contains endemic elements and ofl"ers examples of remarkable disjunc- 

 tions. It must have originated from extinct faunas of neighbouring continents if 

 not of submerged lands. The only natural agent capable of transportation is the 

 wind, but Brinck is convinced that "at present no beetles are invading the islands 

 by natural means" (p. 103), and the reason is not adverse conditions, for several 

 species, introduced with the human traffic, have become naturalized. The unavoid- 

 able conclusion is that dispersal agents, man excepted, are insufficient — and they 

 were the same in the past. The original beetle fauna has survived from pregla- 

 cial time, an hypothesis that nobody would feel inclined to reject, but it does 

 not help us to understand by what means it was able ever to arrive. The weevils 

 of Hawaii have had a long way to come; according to ZIMMERMAN the ancestors 

 as a rule came from the south Pacific or Indo-Pacific regions. Generally he regards 

 also the peculiar genera to have originated in Hawaii or, eventually, in one of 

 the lost islands serving as intermediate stations, but among the weevils are some 

 that defy all explanations: 



