A REVISION OF THE NORTH AMERICAN ICHNEUMON- 

 FLIES OF THE GENIUS MESOSTENUS AND RELATED 

 GENERA 



By R. A. CusHMAN 

 Of the Bureau of Entomology, United States Department of Agriculture 



Ashmead's tribe Mesostenini was separated off from the Crj-^tini on 

 the basis of the small alar areolet (fig. 6) of its members and an in- 

 definable general appearance or habitus. As I have heretofore 

 pointed out ^ I cannot agree with Ashmead and those who follow him 

 that these differences are of sufficient strength to justify the separa- 

 tion. Certain of the genera, which, because of the small areolet, 

 must be placed in the Mesostenini if that tribe is maintained are much 

 less closely related to Mesostenus than to other genera in which the 

 areolet is large. For example, the new genus, Agoywcryptus^ de- 

 scribed beyond, is very closely related to Echthrus Gravenhorst and 

 to certain Oriental genera (for example, Megacryptus Szepligeti,and 

 Torhda Cameron) in clypeal, tibial, and abdominal characters, where- 

 as only its small areolet allies it to Mesostenus. 



The insects here treated constitute the North American representa- 

 tives of the tribe Mesostenini of Ashmead. 



KEY TO GENERA TREATED 



1. Spiracles of first segment before middle ; front tibia in female inflated and 

 basally constricted ; seventh tergite in female much longer than sixth, 

 eighth long and scoop-shaped ; head narrowed beliind eyes, the temples 

 narrow, clieeks swollen and much broader than temples ; clypeus broadly 

 truncate, not medially dentate; mandible with lower tooth larger and 

 longer than upper ; propodeum long, with two transverse cai'inae ; first 

 tergite in female short and stout, hind tibia nearly or quite a half longer 

 than femur, longer calcarium not reaching middle of basitarsus ; tarsus 

 shorter than tibia, apical joint hardly as long as second ; ovipositor much 



shorter than abdomen (figs. 2a, Zh, Qa, 7) Agonocryptus, new genus. 



Spiracles of first segment at or behind middle ; not agreeing entirely 

 otherwise with above 2 



* Joum. Wash. Acad. Sci., vol. 15, 1925, p. 389. 



No. 2761.— Proceedings U. S. National Museum, Vol. 74, Art. 16 



5927—29 1 1 



