xc FAUNA HAWAIIENSIS 



any other large genus of the Hawaiian insects. It is sufficiently proven by the fact 

 that, except in a few special cases, the species have been accurately determined from 

 my tables by those who either have had no previous knowledge of Hymenopterous, or 

 even of any insect characters, after a very small amount of study. I do not think that 

 any such result is possible with most other large Hawaiian genera (or groups of allied 

 genera) such as are found in the Carabidae, Anobiidae or Nitidulidae for instance. 



The Odyneriis nigripennis group is probably of Asiatic origin, and I suspect is an 

 ancient or primitive type, showing some affinity to the genus Rhynchium, in which the 

 species above mentioned was originally placed by Holmgren. 



Species of Odynerus are almost ubiquitous throughout the islands, though some of 

 the densest and wettest boggy forests are absolutely devoid of them. At the same time 

 a slight change in these, made by the incursion of cattle, is sufficient to allow of some 

 species becoming established, where previously they could not exist. A minority of the 

 species such as O. nigripennis, O. obsctire-punctaius and others can occupy most diverse 

 stations, from the coast to the region of frequent frosts in the high mountains. Some 

 others thrive equally on the coast or in open areas in the forest region, or above the 

 forest, but not in the thick forests. On Hawaii some of these pass from above the 

 forest to the lowlands through the midst of the densest woods by means of the almost 

 bare lava flows, by which the woods are intersected, but do not enter the forest on either 

 side of the flow. Some, like O. nigripennis, are not affected by the diversity of station 

 occupied, but others, like O. scoriaceus, have a tendency to local variation in colour, 

 when subject to great difference of climate. Many of the species are true forest insects, 

 some being confined to the drier and more open woods, others are only found amongst 

 denser growths, with heavier rainfall. Some species occur high above the forest limit 

 in the region of frequent frost, and of snow in winter time. Many are fond of frequenting 

 the rocky mountain streams, not only for the purpose of drinking the water, but because 

 they are enabled in dry weather to find there earth sufficiently moist for forming (in 

 some species) or for closing their cells. At one time when camping on Maui at an 

 elevation of about 9000 ft., where owing to the black lava sand and the bright cloudless 

 sky the heat was intense by day, though below freezing point at night, it was interesting 

 to watch two or more species of Odynertis visiting one of the water-holes, situated in so 

 perfectly shaded a spot, that the water retained an icy coldness. After a copious drink 

 of this water, each wasp would fall into a state of complete insensibility by the side 

 of the water-hole, and as many as a score were observed in this torpid condition at the 

 same time. After a considerable period, sensibility would return, and the wasps fly ofi" 

 without apparent injury. 



In the forests these wasps are frequently taken on flowers, especially those of 

 Metrosiderus, but they have been noticed on many other native trees. In general, 

 however, they will be observed flying round foliage of trees and ferns, the females more 

 slowly, while seeking for their prey, the males more wildly, in search of their females. 



