THE NORTH AMERICAN ICHNEUMON-FLIES OF THE 

 TRIBE ACOENITINI. 



By R. A. CUSHMAN AND S. A. ROHWER, 



Of the Bureau of Entomology, United States Department of Agriculture. 



INTRODUCTION. 



This paper is a revision of the tribe Acoenitini as defined by 

 Cushman and Rohwer^ and as represented in tlie North American 

 fauna. Of the five genera inchided only two, Coleocentrus Graven- 

 horst and Arotes Gravenhorst, are known to occur in our region and 

 only these two are treated at length, though all five are tabulated in 

 the key to genera. Coleocentrus has been revised by the senior author 

 and Arotes by the junior author, and new species should be ascribed 

 to the individual responsible for the descriptions. 



The present study is based on examination of all the available types 

 of described North American species of Coleocentrus and Arotes and 

 the rather extensive representation of these two genera in the collec- 

 tion of the United States National Museum, together with specimens 

 of the genotypes of all three of the extralimital genera. 



The illustrations used in this paper were made from drawings pre- 

 pared under the writers' supervision by Miss Mary Carmody, formerly 

 of the branch of Forest Insects, Bureau of Entomology. 



Tribe ACOENITINI Cushman and Eohwer. 



The members of this tribe are medium-sized to large insects chiefly 

 remarkable for the extreme vomeriform hypopygidium in the female. 

 In this respect they are distinct from all other Ichneumonidae. Aside 

 from this the tribe is rather closely allied to the more typical ichneu- 

 monine tribes Rhyssini, Xoridini, etc. 



The members of this tribe, so far as their host-relations are known, 

 are parasitic on wood-boring coleopterous, hymenopterous, and lepi- 

 dopterous larvae. 



Tribal characters.— Head transverse, broad behind eyes; eyes not 

 emarginate within, parallel or nearly; malar space distinct; mandibles 

 bidentate apically, teeth subequal; occipital carina complete; scutum 

 longer than the propodeum, but not especially lengthened, never 



» Proc. U. S. Nat. Mus., vol. 67, 1920, p. 395. 



Proceedings U. S. National Museum, Vol. 57— No. 2320. 



503 



