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



black, while the female is sometimes entirely black. The 

 yellow-banded Crabros on islands other than Kauai are 

 generally found in the open country where the yellow-banded 

 Odyneri occur." November l-~>, 1911. 



It is clear that the colour phenomena exhibited by our 

 Hawaiian Hymenoptera are similar to those seen in other 

 countries (whether in the Hymenoptera or in other orders) 

 where such colour groupings are explained as being associ- 

 ations of inedible species, which are easily recognised by 

 predatory enemies from their similarity of colour. Whether 

 this explanation is true of the Hawaiian case is I think 

 very doubtful, though T do not doubt that a satisfactory 

 explanation of the latter would also explain the others. 

 The Australian Eumenidae, Prosopidae and Fossorial wasps 

 furnish instances very similar to the Hawaiian, and in the 

 same groups, as I have myself observed in the field, in 

 that country. 



If we assume that these Colour-groups are formed by pro- 

 cesses of natural selection and are indicative of inedibility, 

 we are perplexed as to the immunity of insignificant forms, 

 which do not attain notably iridescent wings or other 

 markings and yet fly round in company with the others 

 and are equally or sometimes more plentiful. 



" If the Miillerian theory be correct, wing coloration is of 

 paramount importance in the Hawaiian groups. It appears 

 to be very suggestive that most of the clear-winged species 

 of bees and wasps are open-country insects. Of course 

 many of the dark-blue iridescent-winged ones mix with 

 these, but then they are also common in the woods too — 

 I mean individuals of a single dark-winged species are 

 common in both situations. 



" There are (with reference to colour of wings) distinct 

 evidences in some Hawaiian Crabronidae, of sexual selec- 

 tion being operative. This again, in connection with 

 Miillerian grouping, might start another distinct line of 

 investigation ! " November 13, 1911. 



The writer collected series of nearly every land-bird on 

 each island and so was able to examine the stomach con- 

 tents of a large number of birds in all, and the finding of 

 but a single Mimesa (in the stomach of the thrush Phaeornis 

 lanaiensis) would not tend to show the Hymenoptera, as a 

 favourite food, in any shape or colour. As a matter of fact, 

 an Aculeate Hymenopterous insect (with rare exceptions) 

 is so unlike that of any other Order by its general appear- 



