HYMENOPTERA 3 



reached them. Yet both Dipterous insects and Lepidoptera must have been well 

 established before the arrival of the predatory wasps. The Megachile amongst the 

 endemic aculeates occupies a position similar to that of the solitary species of Coi~uus, 

 and Buteo amongst the endemic land-birds. 



iv. The Heterogyna, or Ants, form a striking contrast to the other groups of the 

 Aculeata. Twenty species are at present known, and these are distributed amongst 

 twelve genera. Nearly all of these are to be found most numerously in the 

 neighbourhood of houses, although some have now spread very widely over the 

 country, and still are spreading. The only one that has any claim to be considered 

 endemic is a species of Pone?-a, {P. perkinsi), which is found only in the mountain 

 forests under logs, and beneath the stones on the margins of the mountain streams. 

 Two other species are not at present known from elsewhere, but of these one, (a 

 Prenolcpis), is known to have been introduced in boxes of earth containing plants, 

 and the other {Poncra kalakanae) has been only taken near settlements, where endemic 

 insects were absent, and it also occurs in the middle of the city of Honolulu. Of 

 the rest, several species form races now described for the first time, but as the e.xact 

 locality whence they have been imported is unknown, it is quite uncertain whether 

 these races have been formed since the time of their importation. We have known a 

 single box of imported plants to contain the winged sexes of three different species 

 of ants. It is not unlikely, however, that the Lcptogeiiys is a natural immigrant, 

 and has arrived in drift-wood, for it frequently nests in the interior of tree-trunks, 

 or beneath tightly-fitting bark. The Ponera, which is alluded to above as being 

 probably endemic, may be classed with the endemic Megachile, as a recent form 

 compared with the rest of the native Aculeates. 



Insular endeniicity. The species of Megachile that is probably endemic has been 

 found on several of the islands, and the endemic Ponera is also distributed over the 

 whole group. Excluding the non-endemic species (amounting to about 27), the two 

 species just mentioned and five Odynerus the localities of which are unknown, there is 

 still left a total of 164 species of endemic Aculeata. 



The proportion of peculiar species to the total number found varies greatly in 

 the case of the different islands, as shown in the followinor table. 



Thus Kauai stands easily first in the peculiarity of its species, and it may further 



I — 2 



