jQ PROCEEDINGS OF THE NATIONAX. MUSEUM vol. 75 



With each genus of the tribe Benibicini I am presenting a key to 

 the species of the genus, including in the key only such species as I 

 have had an opportunity to study from mounted specimens. In a 

 great many cases I have had only one specimen of a species from 

 which to derive characters to be used in separating that species from 

 other species of the genus included in the key. Any key so con- 

 structed must of necessity prove faulty, since color characters, on 

 which we are so often forced to rely in separating species, often 

 vary widely within the species, and since, in the case of some species, 

 even structural differences are not constant. Defects arising out of 

 these difficulties will be found most abundant in the key to the species 

 of the genus Bemhix, wherein I have disregarded geographical dis- 

 tribution on the theory that if two wasps belong to different species 

 there should be some way of distinguishing one from the other aside 

 from their geographical origin. I am fully aware of the imperfec- 

 tions in these keys, but I am submitting them as the best I could devise 

 from the material available. I, therefore, ask of those who may 

 attempt to make use of them a full measure of their generous sym- 

 pathy, and to those who may find them intolerably bad I shall look 

 with expectancy for a speedy publication of something better. 



To the following institutions and to those connected with them 

 having charge of their collections of Bembicine wasps I desire to 

 acknowledge my indebtedness for the loan of material and for sug- 

 gestions and assistance in the preparation of this paper: The Cali- 

 fornia Academy of Sciences, Carnegie Museum in Pittsburgh, Cor- 

 nell University, Massachusetts Agricultural College, Academy of 

 Natural Sciences of Philadelphia, Zoologisches Museum der Uni- 

 versitat. Berlin, American Museum of Natural History, Kansas 

 University, and the United States National Museum. 



Throughout the studies connected with the preparation of this 

 manuscript I have ]'eceived helpful suggestions from Mr. S. A. 

 Rohwer. of the Bureau of Entomology, United States Department 

 of Agriculture, an'd wish to express my gratitude to him. I also 

 wish to give credit to Miss Eleanor T. Armstrong, of the same bu- 

 reau, for the preparation of most of the illustrations which are 

 included in the manuscript. 



DESCRIPTION OF SPECIES 



Hymenoptera belonging to the two tribes, Stizini and Benibicini, 

 which seem to me to form a subfamily, Bembicinae,^ may be dis- 

 tinguished from all other members of the order by the following 



3 This agrees with the arrangement proposed by Rohwer, Bull. 22, Conn. Geol. Nat. Hist. 

 Surv. (1016), 1917, p. 601, except that it excludes the genus SpJieciiis and reduces the 

 ;;roup from family to subfamily rank. 



