86 HYMENOPTERA. 



this and other collections. On the whole this is the largest 

 amount of material in this genus ever collected for study in 

 America. 



An examination of these large series of specimens soon 

 made it evident that very little could be accomplished by the 

 methods of the early students. Up to this time all the de- 

 scriptions of American Prosopis had been based entirely on 

 external characters, usually color or sculpture, and without 

 any figures whatever, except in one or two species. Further 

 than this many of the species had been described from only 

 one or two specimens, distinguished by some minor differ- 

 ence in markings or puncturation. As a result the entire 

 genus was thrown into confusion, and any work done re- 

 cently made doubly difficult by the diificulty of recognizing 

 the early "species". In fact many of these can only be 

 identified by an examination of the types, and in some cases 

 where the types are lost, even this is impossible. Little 

 weight, therefore, could be given to published descriptions 

 as a whole, and much of the work of preparation has been 

 done in accumulating a series of reliably named specimens 

 for reference. This has been quite successful, considering 

 the fact that very few named specimens of some species are 

 in existence, and a few are found only in European collec- 

 tions. Except for a few of the oldest, which are in Europe, 

 and a few of the later ones which are known only by their 

 unique types, I have examined specimens of a very large 

 part of the described species. For this privilege I am espe- 

 cially indebted to Messrs. Swenk and Cockerell, who have 

 given me access to the entire collections of the Universities 

 of Nebraska and Colorado respectively, which contain a num- 

 ber of the types. From this material I have been able to 

 bring together a study collection including almost all of the 

 known species. Others not actually examined and not easily 

 recognizable have been treated separately as "Uncertain 

 Species." 



At no previous time in the history of American Hymenop- 

 terology has anyone made any serious attempt to treat the 

 American species of Pj-osopis as a whole. Previous work con- 



