the Study of the Drepsinididse. 677 



is of importance is rendered more likely from a consideration 

 of the Drepanines of Kauai; at tlie other end of the group of 

 forest-clad islands. Kauai, it is true, has no peculiar 

 generic forms, although geologically so much more ancient 

 than the large island; but being the most distant of the 

 group, as well as at one extremity of the series of islands, its 

 two species of Chlorodrepanis are by far the most isolated, 

 its Hemignathus and Lo.xops are similarly circumstanced, 

 while in the Meliphagines its Moho is very different to the 

 other forms, which are closely allied inter se, and in the 

 Turdidffi it has the two extreme forms of Phceornis. No 

 doubt its small area and comparatively constant climate tend 

 to render it much less rich in Drepanines than Hawaii. 



11. Extreme Specialization of many Forms of 

 Drepanine Birds. 



If, as is natural, we consider the primitive form of Drepanid 

 to have been structurally very similar to such birds as are 

 now comprised in the genera Himatione and Chlorodrepanis , 

 and side by side with these place such forms as LoxojJS, 

 Drepanorhamphus, Heterorhynchus, and Chloridops, the 

 remarkable specialization of the latter is at once apparent, 

 though we are still able to examine connecting forms. To 

 me this specialization indicates the severe competition that 

 has taken place between the Drepanines in past ages. When 

 a vast portion of the food-supply was derived from the 

 blossoms of flowers, and this source of food, as I have shown, 

 was relatively small to what it became later, change to a 

 purely insectivorous, or largely frugivorous, diet must have 

 been very advantageous to the individuals concerned, and 

 the greater the specialization which resulted in obtaining 

 some particular food (provided that it was sufficiently 

 abundant), the greater the advantage to the species. To 

 the field-naturalist who has examined many specimens of 

 such a form as Pseudonestor at various seasons and found 

 that its food consists essentially of the larvae of a group of 

 longicorn beetles peculiarly Hawaiian, and not less remark- 

 able than the Drepanids themselves ; who has seen how 



