Colour-groups of the Hawaiian Wasps, etc. 681 



of species in big genera. We have found no representative 

 so far of Chelodynerus, none of the ' nautarum,' de Sauss., 

 group of Odynerus (probably one of the most ancestral), 

 and it has no peculiar structural group, so that probably 

 the groups of Odynerus in the islands were already formed 

 before the genus chanced to reach Kauai, and some have 

 not yet reached it. This is likely to be the case from a 

 consideration of the beetles ; for the Carabid Cyclothorax 

 (s. 1.), now split into several genera, is unknown on Kauai, 

 very poor on Oahu, the next island, very rich on the inter- 

 mediate islands, and rather rich on Hawaii at the other 

 extremity. This fact alone, without appealing to the geo- 

 logical reasons, is sufficient to disprove Lord Walsingham's 

 conclusion that the islands were once a larger continuous 

 land-area. (See also p. 697.) " Nov. 15th, 1911. 



In Oahu are four Colour-groups, two of which (II and 

 III) may be said to be peculiar to this island. 



Group I. Black insects with dark wings, showing 

 conspicuous blue or purple reflections. 



0. nigripennis, Holmgr., epipseustes, erro, iopieryx, mont- 

 anus, Sm., honanus, unicus ; Nesodynerus optabilis and 

 rudolphi, Dalla Torre. 



Group II. Generally small species, black with shining 

 fuscous wings : no blue reflections. In this group some 

 species show feeble and variable pale abdominal bands, 

 and others some red markings apparently tending to 

 disappearance, and not conspicuous. 



0. dubiosus, Sm., threnodes, pterophaennes, waianaea.nus, 

 paludicola, paranaias ; Nesodynerus oblitus and acyanus. 



" The differences between species of the same genus 

 which enter different Colour-groups are well seen in 

 Nesodynerus. Thus N. rudolphi (I) is very common and 

 ubiquitous, frequenting both forest and open country, 

 while N. oblitus (II) is also abundant, but only occurs in 

 localities — never forests — in which the very common 

 species of Odynerus, viz. dubiosus, etc. (II), are found." 

 Nov. 15th, 1911. 



Group III. Insects usually much marked with red, 

 and the body with appressed fuscous tomentum. Wings 

 to a large extent hyaline and with no blue reflections. 



0. pseudochromus, pseudochromoides, leiodemas, homoc- 

 ophanes, eucharis, oahuensis, Dalla Torre. 



On one occasion all the six members of this group were 

 taken in the same spot and on the same day. 



