CHARLES W. METZ, 85 



A REVISON OF THE GENUS PROSOPIS IN 

 NORTH AMERICA. 



BY CHAS. W. METZ, 



Pomona College, Claremont, California. 



(Plates II-IX.) 



The genus Prosopis is represented in North America by 

 a group of small, very nearly related bees, showing thru- 

 out a remarkable homogeneity in form and structure, but at 

 the same time an almost infinite variability in many sculp- 

 tural and color characters. The genus is widely distributed 

 over the entire United States and far into Canada, being per- 

 haps best represented in the high mountainous States of the 

 Middle West. Representatives may be found in almost any 

 locality that is not entirely devoid of vegetation, but the in- 

 dividuals are seldom abundant. Apparently each species 

 appears thruout its range during a given restricted season, 

 corresponding to the time of blossoming of certain flowers, 

 but too scant investigations have been made so far, to give 

 any definite data. Ordinarily specimens can be found during 

 the summer months from June to September, in most States. 



The present paper is based very largely upon a collection 

 of about six thousand specimens accumulated for this pur- 

 pose. This collection contains series from practically all the 

 localities in which collecting in this genus has been done. 

 The accompanying map shows the approximate range covered 

 by the material. So far as I know it contains a very large 

 proportion, probably three-fourths, of the specimens avail- 

 able in American collections. Most of it is from the collec- 

 tion of Professor C. F. Baker, of Pomona College; for the 

 remainder I am indebted to Messrs. Cockerell, Swenk, Nason, 

 Lovell, and Viereck, who have either loaned or exchanged 

 specimens from their collections, and hearty thanks are due 

 these gentlemen, since without their aid this paper would 

 have been impossible. The C. F. Baker collection contains 

 most of the Baker material from the U. S. National Museum, 

 as well as many cotypes of species originally described from 



TRANS. AM. ENT. SOC, XXXVII. (H*) 



