680 Mr. R. C. L. Perkins on the 



separated in structure. Sometimes the yellow band 

 appears only on the ventral surface. The phenomena are 

 precisely identical with those observed in the Crdbronidae 

 (see p. 688), and, I think, are explicable in the same way. 

 The blackness of so many Hawaiian Eumenids has been 

 produced in the islands and the abnormal individuals are 

 reversions to a former general condition in colouring. The 

 Eumenids, furthermore, like the Crabronids, have retained 

 in some species the original yellow-banded coloration. 



The general tendency to blackness of the Hawaiian 

 Aculeata, as a whole, is one of their most remarkable 

 features. The blackness of these insects is increased by 

 the dark colour of their wings, which, in a large number 

 of the species, exhibits striking blue or purple reflections. 



" My original paper * on colour of Hawaiian wasps was 

 written too early to have much value. I treated only the 

 Kauai species as conspicuous on account of the pale bands. 

 This was an error ; all the things I send as examples are 

 conspicuous in life : they are the conspicuous feature among 

 the day-flying insects in the islands and about the only 

 one, except at special times and places." Nov. 8th, 1911. 



The following Colour-groups — entirely different from 

 the groups based on structure and real affinity — are 

 distinguished in the Introduction. 



On Kauai are two Colour-groups, one of which contains 

 only two known species. 



Group I. Insects with much red marking, wings 

 shining fuscous, when spread. 



0. hlacMnrrni, Kirb., and soroo' : allied species. 



Group II. Black insects with two conspicuous whitish 

 or yellow bands f on abdomen ; wings dark and with 

 conspicuous blue or purple reflections. Fourteen species 

 of diverse structure. 



" Kauai is the most northern of the forest-bearing 

 islands, and it has by far the widest channel between it 

 and its next neighour — Oahu. The specific characters of 

 its species are usually the most striking^of those exhibited 

 on any island, but it lacks representatives of many ' groups ' 



* Proc. Phil. Soc. Cambridge, vol. ix, Pt. VII (1897), p. 378. 

 The examples alluded to were exhibited to the Entomological 

 Society, May 1st, 1912 (Proceedings, pp. Ivi-lxv). 



t " When the insects are on the wing, these bands are clearly 

 seen." — R. C. L. Perkins, in Proc. Phil. Soc. Cambridge, vol. ix, 

 Pt. VII (1897), p. 378. 



