xcii FAUNA HAWAIIENSIS 



constantly visited by the female of this wasp. She would keep running from one end 

 to the other of the gallery of the caterpillar, as the latter retreated to and fro, until 

 perhaps after dozens of these pursuits, the prey would drop down into the herbage 

 below, to be at length found, stung into paralysis, and carried away to the cell. Several 

 species of the wasps have been seen to carry off the grass-eating enemy of sugar-cane, 

 O. accepta, and O. epipsetistes preys on that of O. cofitinuatalis. In fact no doubt almost 

 any Omiodes caterpillar is acceptable to many of these wasps, for we have seen them 

 visiting the plants of Astelia near the volcano at Kilauea in search of the species that 

 feed on these. Of other Pyralid caterpillars various species of Phlyctaenia, Pyrausta 

 litorea, and others, Mecyna, and the foreign Hymenia recurvalis are all well-known prey, 

 so that it is probable that most Hawaiian species of this group fall victims on occasion. 

 Of smaller moths the caterpillars of Tortricidae and Carposinidae are favourites. 



It is a common sight to see Nesodyjierus rudolphi and other species that are 

 common on the lowlands, extracting the larvae of Crocidosevta plebeiana from the flower- 

 buds of Sida ; in fact this Tortricid now furnishes an important food-supply of the 

 larvae of various littoral and sub-littoral species of wasps. In the mountains Eccoptocera 

 foetorivorans is a common prey. Besides these and other Tortricids, endemic and 

 foreign, and various Carposinidae of the genus Heterocrossa, members of the Tineina 

 are also preyed upon, e.g. the Gelechiid Thyrcopa, as well as introduced forms. With 

 this range of choice in the nature of the prey, the number of caterpillars stored in a cell 

 varies very much ; over thirty of a Carposinid or small Tortricid (I failed to note which) 

 were once found in one made by O. oahuensis. 



In many localities at favourable seasons the number of individuals that are seen is 

 extraordinary. On one occasion I visited a mountain gulch on Molokai nearly every 

 day for three weeks and I estimated that in a length of a couple of miles (below the 

 line of forest) the population of adult wasps in this length was at least one million. 

 Five or six species were represented, but two or three were much more numerous than 

 the others. I have noticed an almost similar abundance in other localities. As may 

 readily be imagined, the economic value of these wasps is consequently very great. 

 This is the more true, since they readily prey on the most injurious imported Tortricines, 

 such as Archips postvittanus and other harmful caterpillars. It is probable that very 

 few of the large number of species existing are really rare, though of some only a few 

 specimens or even single examples have been taken. The Oahuan forms have been 

 much studied, and the only one that has been found once only is Nesodynerus optabilis, 

 and it must be remembered that the general appearance of this insect is exactly that of 

 several of its commonest allies, so that it may readily be passed over. Excepting the 

 littoral or sub-littoral species and the one just mentioned, every known Oahuan Odynerus 

 has been found in the mountains within three or four miles of Honolulu itself, as one 

 might say in one spot. Some, however, are of course much rarer than others, and their 

 apparent rarity is increased by the fact that, like Aculeates in other countries, they are 



