the Study of the Drepanididae. 569 



becomes manifest, and this cause lias produced Hemignathus 

 in the one, and DrejJanis in the other, so like one another in 

 general structure, while really but remotely allied. How 

 easily the extraordinary lengthening of the bill, to which the 

 resemblance is mainly due, may have taken place, side by 

 side with the increasing length of the tubular flowers, is 

 apparent from the fact that in some of the species there is 

 even now individual variation in this respect. It should also be 

 stated that in immature specimens the beak is much shorter, 

 and that in the freshly-hatched young of Chlorodrepanis 

 it is a short wide member, instead of having a slender 

 curved form as in older birds. In the long-billed forms 

 the mandibles are almost invariably shorter in the more 

 "conservative^' females, which in my second group retain 

 in the adult the more primitive coloration of the young, 

 though the males assume a totally diff'erent dress. 



5. Transition from a largely Vegetable Diet to pur el ij 

 Animal Food. 



Of the genera Loxops, Oreomyza, and Heterorlujnchus the 

 members are mainly insectivorous, but each comprises some 

 species which at times feed on the nectar of flowers. In 

 Loxops and Heterorhynclms the tubular character of the 

 tongue is fully preserved, yet they very rarely feed from 

 flowers, and some of the species perhaps never do so. Certainly 

 that of the latter genus which is found on Hawaii is purely 

 insectivorous, feeding, after the manner of a Woodpecker, 

 on beetles and other insects; but the other three allied 

 species are less adapted to such a life, and the Maui form has 

 been known to me to visit blossoms as a very rare occurrence, 

 while the partiality that the extinct species of Oahu had for 

 banana flowers was often noticed. That these birds, even 

 when purely insectivorous, still retain the characteristic 

 Drepanid tongue, is clearly due to the fact that it remains 

 a most efficient organ for obtaining insect food — ^in 

 Heterorhynchus for extracting the wood-boring beetles of 

 which it is so fond ; and in Loxops for securing caterpillars 

 which live in the terminal buds of some forest trees, not to 



