INTRODUCTION Ixxiii 



Review of the Hymenoptera. 



The Hawaiian Hymenoptera are remarkable for the extreme paucity of the number 

 of families of this vast Order, that are represented by endemic species. The saw flies 

 or Phytophaga, considered by some as a sub-order, are totally unrepresented. Ashmead 

 in 1900 recognized 94 families in the Hymenoptera, and this number may be taken as 

 approximately correct, for while some of these groups are in our opinion unworthy to 

 rank as families, yet others are formed of discordant combinations of genera, which he 

 freely admits are of quite different ancestral origin, and a proper classification of these 

 will make good any loss in number caused by the sinking of groups, that he considered 

 as distinct families. 



Excluding forms that are known to be introduced, or from various kinds of 

 evidence are almost certain to prove so, the endemic Hymenoptera represent only the 

 following families : (i) Prosopidae, (2) Crabronidae, (3) Pemphredonidae, (4) Eumenidae, 

 (5) Bethylidae, (6) Poneridae, {7) Proctotrypidae, (8) Diapriidae, (9) Scelionidae, 

 (10) INIymaridae, (11) Figitidae, (12) Miscogasteridae, (13) Encyrtidae, (14) Pteromalidae, 

 (15) Eulophidae, (16) Ichneumonidae. (17) Braconidae. Moreover of these 17 families 

 four are only represented by a single species that can really claim endemicity (Poneridae, 

 Proctotrypidae, Pteromalidae, Braconidae), so that these can be looked upon as com- 

 paratively recent additions to the endemic fauna. It will be seen that I have excluded 

 a number of families, which contain species not at present known outside the islands, 

 and it is possible that a few of these species are really endemic, though I think this 

 is unlikely. 



I will now refer to those more or less doubtful species which cannot positively be 

 considered as foreign importations, as well as to some of those that are without doubt 

 of human introduction. In the latter class are Xylocopa brasilianornvi (aeneipennis), 

 RIegachile palmarttm^ and M. scJiaiiinslandi^, and Apis mellifica amongst the bees. 

 Only two of these insects, the Xylocopa and Apis, occurred to Blackburn, when collecting, 

 and as the two Megachilc are very common Honolulu insects and, further, have spread 

 widely thence in the last 1 7 years, we can be sure they have been imported and were 

 not present in the islands even 30 years ago. Apis and Xylocopa are of earlier intro- 

 duction, the latter being well known to have been non-existent here till long after the 

 settlement by foreigners. It was no doubt brought from the warm parts of America, 

 when formerly ships visited the islands frequently from that region. In the Fossorial 

 group an American Stigmus was once taken in the middle of the town of Honolulu and 

 appears to have not established itself while a Sceliphron of early introduction from 

 America (known, however, not to have been present before the foreign settlement) and 

 a Trypoxylon of recent importation from China, are now both widely spread and 

 thoroughly naturalized. Both these insects are semidomestic in habits. 



' The former of these is now known to me from California, the latter from China. 

 F. H. I. k 



