198 MESSRS. T. BLACKBURN AND P. CAMERON ON THE 



Dr. Sharp* divides the coleopterous fauna of the islands 

 into three divisions : first species (chiefly cosmopolitan) 

 introduced in stores, hallast, &c., by commerce ; secondly 

 species introduced hy natTiral currents in drift-wood, &c. ; 

 and thirdly endemic or autochthonous species, the latter 

 being distinguished from the second by structural pecu- 

 liarities, being to all appearance forms of great antiquity, 

 the distinction between the two groups being owing, no 

 doubt, to the fact that the autochthonous species were 

 introduced into the islands at a much more remote period 

 — so remote, indeed, that their nearest allies have become 

 extinct, or nearly so, on continents, where the struggle for 

 existence has been much keener. 



My knowledge of the Hymenoptera is not sufficient to 

 enable me to separate the species which belong to Dr. 

 Sharp^s two last categories ; yet I have no doubt at all 

 that most of the species of Crabro, Odynerus, and Prosopis 

 have originated in the islands by evolution from one or 

 two species introduced at some remote period into the 

 islands by currents on drift-wood. The aculeate species 

 found in the Archipelago belong to genera which we might 

 a priori expect to find there, being species which form 

 their nests in or on wood, the genera which nidificate in 

 the ground being absent. 



The following species have, I believe, been introduced 

 by man^s agency : — Camponotus sexguttatus, P oner a con- 

 tracta, Monomorium specularis, Tetramorium guineense, 

 Prenolepis longicornis, Pheidole megacephala, Solenopsis 

 geminata, all ants of wide range. Pelopceus cmmentarius, 

 Polistes aurifer, P. hebraus, Xylocopa (sneipennis, Evania 

 IcEvigata, Metacoelus femoralis, and Spalangia hirta. 



It is possible that P. hebrceus may belong to Sharp's 

 second group, but I have no doubt that P. aurifer and the 

 * Scieut. Trans, of the Eoy. Dubl. Soc. iii. p. 269. 



