ICHNEUMON-FLIES OF AMERICA: 1. METOPIINAE 171 



Front wing 2.7 to 7.5 mm. long; body punctation rather fine; com- 

 bined face and clypeus strongly convex but of various kinds of con- 

 vexity according to the species; upper margin of face produced as a 

 triangular point between bases of antennae, this triangular point with 

 a median vertical carina behind, which continues between antennal 

 sockets to base of frons; frons without a median process, except in 

 certain Oriental species which have a median compressed ridge on 

 frons; temple flat to strongly convex, usually rather long, so that the 

 head is subcubical; cheek usually about 0.5 as long as basal width of 

 mandible; mandible strongly tapered toward apex, its lower tooth 

 much smaller than upper tooth; areolet absent; intercubitus separated 

 from second recurrent by about 1.2 its length; nervulus sometimes 

 interstitial but usually postf ureal, usually strongly postf ureal; nervel- 

 lus strongly inclivous, broken near its lower 0.2; prepectal carina com- 

 plete, its upper end joining front end of subtegular ridge; sternaulus 

 usually absent or indistinct, rarely present as a short sharp impression; 

 metapleurum polished, impunctate, or sometimes with a few scattered 

 punctures; propodeum usually almost or quite completely areolated, 

 the costula frequently absent, the median basal area and areola often 

 confluent, and sometimes other carinae lacking; propodeal spiracle 

 elongate; legs stout or very stout; base of hind coxa not or weakly pro- 

 duced behind its socket so that there is little or no basal shoulder on 

 hind side; second trochanter of front and middle legs almost or quite 

 completely fused with its femur; front spur of middle tibia shorter 

 than hind spur, except in an Australian species, usually very much 

 shorter than hind spur; tarsal claws apparently simple; abdomen 

 parallel-sided or tapered toward base; first tergite at base rather nar- 

 row to broad, its spiracle near its basal 0.3, its lateral longitudinal 

 carina strong to apex, its median longitudinal carinae strong basally, 

 but not reaching apex; second tergite without dorsal carinae; epipleura 

 of first two tergites vestigial, of third and following tergites rather 

 wide; seventh tergite not retracted in either sex; female subgenital 

 plate weakly sclerotized, not specialized. 



The genus Exochus is worldwide in distribution and is the largest 

 genus of the subfamily. It is especially well represented in deciduous 

 woods of the Northern Hemisphere. We have divided the Nearctic 

 species into a number of species groups, to facilitate the comprehension 

 of their characters and relationships and to simplify the problems of 

 specific descriptions. There are additional species groups in other 

 parts of the world. The genus in the broad sense in which we use it 

 contains a rather miscellaneous assemblage of species, but one which it 

 would seem unwise to subdivide into genera or subgenera because of 

 the necessity to recognize about a dozen genera or subgenera for the 

 assemblage if it were subdivided at all, some of which would be very 



