1897.] Mr Perkins, Notes on some Hawaiian Insects. 377 



The only other species examined is P. aequalis, a species very 

 distinct from any of the preceding, found on the Island of Kauai. 



The variation in this species is similar in kind to that of P. black- 

 burni, but the relative numbers of each variety are very different, 

 for while in that species the red-legged variety is extremely rare, 

 in the present one out of 181 examined no less than 70 are of this 

 form. The large amount of variation exhibited is the more 

 remarkable on account of the limited distribution of the species, 

 for not one of the genus is known to inhabit more than one 

 island, and many of them are certainly confined to a very small 

 area of the island on which they are found. 



It has been already mentioned that all the species are polyga- 

 mous. Of selective pairing by the different varieties there is no 

 trace. On one occasion when watching a number of P. varians 

 on a fallen tree trunk, I noted that a female of the black-legged 

 form paired successively with the brightly coloured variety, which 

 has the apices of the femora red, then with one of her own 

 colour, and shortly afterwards with the extremely rare variety 

 which has the legs entirely dull red. — And instances of a similar 

 kind can be noticed any day, where a species is plentiful. Were 

 sexual selection operative there is no doubt that a much larger 

 number of distinct forms would be produced. It is interesting to 

 consider the conditions that have brought about the specific dis- 

 tinctions in these species so closely allied. Taking into considera- 

 tion the fact that no species is found on more than one island, 

 either geographical isolation, or a difference in food, or a combina- 

 tion of these two factors, seems to account sufficiently for the 

 separation of the species. Of the species under consideration, 

 three may be found side by side (although each of them is also 

 found in places apart from the other two), yet each keeps entirely 

 to the tree on which its larva feeds ; and the other P. blackburni, 

 although it has the same food as P. damvinianus, does not inhabit 

 the same area. 



So far as the native fauna is concerned these Plagithniysi 

 have few enemies. It is doubtful whether any parasites attack 

 them ; if any do so, they are certainly of extreme rarity. Except 

 on the Island of Maui, birds either leave them alone or perhaps 

 are very rarely able to catch them. On that island, however, one 

 of the Drepanididae — Pseudonestor — is extraordinarily modified in 

 accordance with its habit of living on the larvae, pupae and 

 immature beetles of this genus and the allied Clytarlus. Indeed 

 its food consists chiefly of these creatures, which it is able to tear 

 out from the hardest wood. The great scars, made on trees which 

 are affected by the beetles, may often be seen as the result of the 

 work of this bird, and when opened its stomach is usually filled 

 with their larvae. 



