Ixii FAUNA HAWAIIENSIS 



derived one from another or at least from forms hardly different from either (PI. XVI, 

 figs. 8, 9 and lo). It might be supposed that the small distance between the islands 

 would not be sufficient for isolation, especially when we consider that the animals, 

 from which all the fauna is derived, must necessarily have traversed the vast distances 

 between the islands and other lands. This, however, is clearly not the case. Certain 

 species, of migratory instinct, amongst the birds visit the islands regularly, but do not 

 settle down and give rise to endemic forms, and the insects of known migratory habits, 

 like the butterflies Pyratneis cardtii and Anosia eripptcs, the foreign species of Plusia, 

 Sphinx convolvuli, Nomophila noctuclla, the large American dragonflies etc. we may 

 well suppose receive recruits sufficiently frequently from other lands to prevent any 

 true isolation. It is what we may fairly call the 'chance' immigrant that is the 

 potential producer of new species. It seems incredible that so strong-winged a 

 butterfly as Pyranieis atalanta, which has been established on the island of Hawaii 

 for over twenty years^ was, at least until a few years ago, certainly restricted to that 

 island, and has not even yet been recorded from any other. As is well known, this 

 same butterfly is supposed to be a constant migrant from the European continent 

 to England across a channel comparable with that between Hawaii and its next 

 neiofhbourinof island. 



If we consider the endemic species, and examine the ' Cyclothorax ' group of 

 Carabid beetles (presumably derived from the Australian region) we find they are 

 very richly represented on the neighbouring islands of Maui and Molokai, central in 

 the group, relatively poorly on Hawaii, with its comparatively great area and varied 

 conditions, much more poorly still on Oahu, and, so far as is known, totally absent 

 from Kauai, the extreme island to the north-west. Though the ' Cyclothorax ' 

 beetles have existed a sufficient time in the islands to become so enormously rich 

 in species and to occupy the most diverse situations, where they occur, yet they have 

 clearly been very slow to spread from island to island. The fan-tailed flycatchers 

 [Chasiempis) derived also from the Australian region, are totally absent from the 

 three intermediate islands, showing well the chance character of the interisland 

 immigration, in the case of birds, whose ancestors also must have traversed thousands 

 of miles of sea to reach the Hawaiian group. In the Drepanididae, Heterorliynchus 

 is unrepresented on Molokai and Lanai, Heniignathus on Maui and Molokai, and 

 Drepanis (incl. Drepanorhamphus) on Oahu and Kauai. Yet such forms must have 

 required enormous time for their evolution. In none of these cases can the nature 

 of the islands, from which the various animals above mentioned are absent, be for 

 a minute considered as the cause of their absence. In the endemic birds I have 

 elsewhere noticed that there are two elements, one consisting of a few wide-ranging 

 species, widely spread throughout the group (e.g. Hiniatione vestiaria and Psittacirostra 



' Though abundant on Hawaii, in districts visited by him, this butterfly was not found by Mr Blackburn 

 some 30 years ago, so I suppose it reached the island subsequent to his visit there. 



