Ixxii FAUNA HAWAIIENSIS 



these immigrants ages to spread over the whole group. Some like the Pterostichine 

 beetles have apparently not yet fully done so. Peculiarity seems often in proportion to 

 the isolation, this roughly depending, in the case of the different islands, on the width 

 of the channels between them. Where we study allied species, Kauai has these as 

 a rule most highly modified. Its ' Oo,' Acrulocercus, is almost generically distinct 

 from the others, its Loxops is the most aberrant, it alone has two species of Phaeornis, 

 one being by far the most aberrant, its ' Elepaio ' {Chasievipis) is the most different, 

 it alone has two distinct species of Chlorodrepanis, the one structurally at one end 

 the other at the other extreme of the series, these birds hardly differing on the other 

 islands. Its Amastrae in the land-shells have produced the most remarkable of all 

 forms in the subgenus Kauaia, and probably from a still earlier immigrant Amastra 

 (or antecedent of Avmslra) has developed the remarkable series of Carelia, the young 

 of which are in many ways so like Amastra itself. I have reason to believe that in 

 many cases, where we now find the greatest variety of allied species of any group of 

 animals, that island is the place whence all the species originated, or in other words the 

 place where the original immigrants became established. It is difficult to compare one 

 group of animals with another, as regards the importance of the modification that exists, 

 but I cannot see in the existing Achatinellidae any greater modification to have taken 

 place than is observable in the present components of the Hawaiian Nitidulidae, or 

 Anchomenine Carabid beetles, or in the Drepanid birds. It is interestmg to note that 

 the island of Hawaii, which is sometimes loosely stated to be the ' youngest ' island, is 

 in my opinion the one on which the last-named birds were first established. But it 

 must be remembered that Hawaii is a composite island, and its northern part is of very 

 great age and existed long prior to the bulk of the island, and coincidently with the 

 oldest of the other islands of the group, so that the Drepanid birds may have reached 

 the northern portion, before the rest rose above the sea. The more recent parts have 

 themselves existed for ages and, when their forests became continuous with those 

 of the original island, it would take a comparatively short time for the whole to 

 be occupied by birds. There is no existing genus of Drepanididae which does 

 not occur on Hawaii (unless the Molokai 'mamo' be considered generically distinct 

 from Drcpanis), excepting the parrot-billed Psendoneslor on the next island, Maui, and 

 the crested Palvieria of that island and Molokai, a form allied to the vagrant Hiniatione. 

 But Hawaii itself, in addition to all the other Drepanid genera, alone has the specialized 

 Ciridops and Viridonia, as well as the three more allied genera, Loxioides, Rhodacanthis 

 and Ckloridops, indicating excessive antiquity of its avifauna. 



