688 Mr. R C. L. Perkins on the 



subsequently found to contain a European species, Prosopis 

 hriecKbaumeri, Forst., and later a Cliinese one. Thus an 

 Asiatic origin is highly probable. The Neso'prosopis are 

 almost the most ubiquitous of any Hawaiian insects. 



Crabronidae. — The Hawaiian Crabronidae are repre- 

 sented by eighteen described species, which I have dis- 

 tributed in four genera. All these forms appear to be 

 closely allied, and, as it appears to me, might well be the 

 descendants of one original immigrant yellow-spotted form, 

 allied to the British Crabro vagus, L. To this latter there 

 are closely allied species in China, if it does not occur 

 there itself, and for this reason an Asiatic origin for the 

 Hawaiian forms may be suspected. Of the eighteen species, 

 three represent each one a distinct genus, while another 

 genus, Nesocrahro, contains four species, so that the greater 

 pai't of the known forms fall into one genus Xenocrabro, of 

 which the others appear to be simply derivatives, and it is 

 to the least remarkable of the Hawaiian species of Xeno- 

 crcibro that the European Crabro vagus is most nearly 

 related. None of the other diverse groups of Crabronidae 

 are represented in the Hawaiian Islands. 



Some of the species are much and conspicuously marked 

 with yellow on all parts of the body, the yellow markings 

 becoming reduced in others, until, in X. mandibularis, Sm., 

 we have an entirely black insect. There is, in the yellow- 

 marked species, much variety in the coloration, and the 

 variation exhibited is often of an interesting character. 



C. distinctus, described by Smith from a Crabro obtained 

 from Hawaii early in the last century, was at first unknown 

 to me, and I suspected a mistake in the locality. Later 

 on, however, I found that Smith's species is an extreme 

 and rare variety of C. notostidus, which is typically a black 

 insect with small yellow thoracic markings. Intermediate 

 specimens between the extremes are much commoner than 

 typical distinctus. This brightly marked form has so far 

 only been found at or near the coast, where the intermedi- 

 ate forms also occur, as well as the variety I called noto- 

 stidus. In the mountains in the forest region the latter is 

 predominant and intermediates are rarely met with. From 

 these facts one might suspect that the hot dry climate of 

 the coastal regions was productive of the conspicuously 

 marked varieties. The following considerations make such 

 an explanation improbable. In the genus Nesocrahro I 



