Ixxxviii FAUNA HAWAIIENSIS 



' reversions ' to an ancestral style of coloration, and I believe this is borne out by an 

 examination of the varieties of other Hawaiian species. In these there is a general 

 tendency to blackness of coloration, some few retaining conspicuous yellow mark- 

 ings, while most have these reduced to inconspicuousness or they are entirely 

 absent. Xenocrabro haivaiiensis and fiilvicriis, Oreocrabro abnorniis and Hylocrabro 

 tiimidoventris, species with normally black abdomen, all become spotted, as excep- 

 tional and sometimes very rare varieties. Species like Nesocrabro stygius and 

 daemonius, with immaculate abdomen above, frequently retain yellow pigment spots 

 beneath, where they are concealed from view. Generally speaking yellow markings, 

 especially thoracic, are less easily lost in the female than in the male. The general 

 blackness of the Hawaiian Crabronids, as now manifested, has I think been produced 

 within the islands, and while some still retain more or less the colour of their ancestors, 

 the majority have greatly departed therefrom, though many of them in exceptional 

 individuals reproduce that coloration to a greater or less extent. Further, a study of 

 the case cited of Nesocrabro rubrocaudatus and Xenocrabro distinctiis lends strong 

 confirmation to the community of descent that is suggested by the consideration of their 

 structural characters. At least I find it difficult to understand how two species of these 

 distinct genera can, under totally different conditions of climate and environment, produce 

 remarkable colour varieties, totally dissimilar to their usual forms, yet almost identical 

 with one another, unless they be reversions to a former style of coloration. 



As in the bees, Hawaii is also the richest island* in its Crabronidae, seven species 

 occurring there, of which five are apparently endemic and one of the others is almost 

 specifically distinct (//. tiiiuidoventris var. Icucognatlms). Maui has six species, but only 

 one is peculiar to it, whilst Molokai and Lanai have none endemic. Oahu, like Hawaii, 

 has seven, but only three are peculiar to it. So far as yet discovered, however, it alone 

 possesses the remarkable genus Oreocrabro. Kauai is poorest of all, with three species 

 only, two of which, Nesocrabi'o compact iis and Xenocrabro vionticola, both occur on Oahu 

 (the former also on Lanai and possibly other of the islands) and one only peculiar to 

 itself, X. affinis. These statements are likely to need modification hereafter, but are 

 based on the information accessible at the time of writing. They do not accord with 

 the facts given in 1899, as might be expected. 



No parasites are known to attack the Crabronidae of the islands, though it is quite 

 likely that the Chalcidoid Encyrtidae may do so, nor did I find any specimens of them 

 in the stomach of the many birds that I dissected. They have a peculiar odour, like 

 members of their family in other countries. 



Tkypoxylonidae. — A family of little importance in our fauna, the Trypoxylonidae 

 are represented by a recently introduced species of Trypoxylo)i, a native of China, 

 occurring also, I believe, in tropical Queensland, and by three species of Pison, of the 

 sub-family Pisoninae. One of these is of quite recent introduction, having become 



