8 PROCEEDINGS OF THE NATIONAL. MUSEUM vol. 75 



KEY TO THE GENBHA OF STIZINI 



1. Posterior surface of propodeum concave, its posterior-lateral angles promi- 



nently compressed and wedge-shaped ; second cubital cell petiolate ; second 



abscissa of the cubitella lacking Bembicinns. 



Posterior surface of propodeum flat or convex, its posterior-lateral angles 

 rounded; second cubital cell not petiolate (rarely subpetiolate) ; second 

 abscissa of both radiella and cubitella present 2. 



2. Inner eye-margins approximately parallel ; mandibles dentate ; second abscissa 



of the radiella at its origin strongly bent forward toward the costal border 

 of the wing; scutellum of the female usually with a small median deprcB- 



sion Stizus. 



Inner eye-margins convergent at the clypeus ; mandibles edentate ; second 

 abscissa of the radiella approximately straight; scutellum of the female 

 without a median depression Stizoides. 



Genus BEMBICINUS Costa 



Figures 3, 4 



Benibicinus Costa, Fauna del Regno di Napoli, vol. 4, 1859. — Patton, Bull. U. S. 



Geol. Surv., vol. 5, 1879, p. 345. — Cbesson, Synopsis, 1887, Supp. vol. Trans, 



Amer. Ent. Sec, p. 115. 

 Stizus Handlibscii (part), Sitz. Akad. Wissensch. Wien, Math.-Nat. CI., vol. 



101, 1892, p. 26.— Fox (part), Proc. Acad. Nat. Sci. Phila., 1894, p. 304.— 



Kohl (part), Ann, des. K. K. Naturhist. Hofmus., vol. 11, 1896, p. 421.— 



Dalla Toere (part). Cat. Hym., vol. 8, 1897, p. 519. 



Genotype. — Vespa tride'ns Fabricius, designated by Patton, 1879. 



Members of this genus can readily be distinguished from those of 

 the other two genera of the tribe by the character of the posterior 

 surface of the propodeum. This is distinctly concave and its lat- 

 eral angles are compressed and more or less prominently wedge- 

 shaped. In this respect members of this genus resemble those of 

 the genus Bicyrtes Lepeletier, but in this latter genus the ocelli are 

 completely reduced to cicatrices. 



Head broad as thorax; eyes strongly convergent at the clypeus; 

 width of labrum approximately double its dorso-ventral length; 

 posterior margin of tenth flagellar segment of the male prolonged 

 into a slightly curved, slender process; posterior surface of the 

 propodeum concave, its posterior-lateral angles compressed and more 

 or less wedgelike; second cubital cell usually petiolate but in some 

 cases the first and second cubital cross veins simply join at their 

 union with the radial or even join the radial separately; mediellan 

 cell subtends only one short vein, which is the second abscissa of 

 the radiella; the first abscissa of the discoidella is much shorter than 

 the width of the submediellan cell ; eighth sternite of the male ends 

 in three spines. 



