Colour-groups of the Hawaiian Wasps, etc. 687 



ance in life, that one can hardly credit any vertebrate 

 enemy with sense enough to distinguish between Colour- 

 groups of these and without the sense to distinguish the 

 class as a whole. 



If Colour-groups in Hymenoptera have arisen as a mark 

 of inedibility, the latter quality can I think have nothing 

 to do with the possession of a sting.* 



At one time 1 1 supposed that the Hawaiian Colour-groups 

 might be the result of the action of climatic differences, at 

 least in so far as these groups were special to certain of the 

 islands. This seems very doubtful, for we find the nearest 

 approach to the Colour-group of wasps living in the forests 

 of Kauai, in those living on the driest coasts of Oahu, and 

 quite absent from its very similar forests. In fact a satis- 

 factory explanation of the Colour-groups of Hawaiian 

 Hymenoptera is wanting, and, when found, will no doubt 

 explain some of the similar phenomena elsewhere. 



It is interesting to trace the structurally allied forms on 

 different islands and see how their superficial appearance 

 is changed by entering different Colour-groups. 



Odynerus eutretus of Hawaii is a black insect with dark- 

 blue iridescent wings ; on Maui, it is represented by 0. 

 homoeogaster, a red-marked wasp ; on Kauai, by 0. mimus, 

 a conspicuously white-banded species. The obscure-punc- 

 tatus group on Hawaii is replaced by the redder species 

 0. sandwichensis and its allies on the intermediate islands ; 

 on Oahu, the blue iridescence of the wings is lost as well 

 as all the red markings (0. dubiosus and allies), while on 

 Kauai, the red markings remain, but the wings are of a 

 shining fuscous (0. blackburni and soror), as in the Oahuan 

 allies. Odynerus nigripennis, ubiquitous over all the other 

 islands, is replaced on Kauai by the equally common, pale- 

 banded 0. radula, F. 



Prosopidae. — All the fifty-three species belong to the 

 single genus Nesoprosopis based on the island forms but 



* Compare Trans. Ent. Soc, 1904, pp. 645-6.— E. B. P. 



t Dr. Perkins is evidently alluding to his paper in Proc. Phil. 

 Soc. Cambridge, vol. ix, Pt, VII, 1897, p. 380, where he argued 

 that the colours are due to " climate or some such cause." He also 

 wrote, November 10, 1911, in reference to the above paragraph in 

 the text : — 



" I did not state other reasons against the ' climate ' view because 

 I hardly thought it worth considering — there are too many impossi- 

 bilities in such a view ! " 



