ICHNEUMON-FLIES — GELINAE : MESOSTENINI 33 



(the usual condition); areolet very small to large, when small some- 

 times open at apex, usually pentagonal or almost square but some- 

 times oblong (especially when reduced in size); first tergite usually 

 rather strongly expanded apically, its spiracle varying from just be- 

 hind the middle to far behind the middle; ovipositor various, usually 

 weakly compressed with a weakly sagittate tip, rarely the tip of lower 

 valve enclosing or partially enclosing the upper valve (as in Dotocryp- 

 tus, Amauromorpha, and Kriegeria), the upper valve without trans- 

 verse ridges and rarely with teeth between its nodus and apex (in 

 these exceptions the ovipositor tip is rather strongly compressed). 



This is by far the largest sub tribe, and the one most diverse in 

 structure, hosts, and biological characters. Its distribution is world- 

 wide. 



Key to the Nearctic genera of Mesostenina 



(Includes also the two Nearctic genera of Baryceratina.) 



1. Frons with a strong sublateral carina extending upward from outer edge of 



antennal socket (fig. 307,a) ; areolet moderately small, approximately rec- 

 tangular, its front side longer than its hind side (fig. 307,a). Subtribe 



Baryceratina, in part Whymperia (p. 22) 



Frons without a strong sublateral carina; areolet various 2 



2. Areolet medium or large, always closed, both its height and width greater 



than six times the width of the bordering veins 3 



Areolet small, often open apically, either its width or its height less than five 

 times the width of the bordering veins. (Hemisphragia, which has an 

 areolet of almost intermediate size, is included here. The single Nearctic 

 species is small, slender, and lacks the brachiella vein (fig. 317, a)) ... 18 



3. Mesoscutum rather weakly convex, broad; notaulus usually absent or short 



(except in Hidryta), seldom extending beyond middle of mesoscutum; 

 thorax short and first abdominal segment elongate, the latter more than 

 half as long as thorax; tergite 2 usually polished and not conspicuously 



punctate. See habitus figures 315, b and 316,a,b 4 



Mesoscutum more strongly convex, usually narrower; notaulus usually ex- 

 tending beyond middle of mesoscutum (but not in Compsocryplus, Lanugo, 

 or Reptatrix) ; second tergite often mat, or evidently punctate, or both mat 

 and punctate (but not in Joppidium) 6 



4. Prepectal carina ending near middle of hind margin of pronotum (fig. 316,b); 



nervulus at or distad of basal vein; prepectus usually with a short, vertical 

 carina opposite lower corner of pronotum; eporaia usually strong; ovipositor 



tip sagittate 17. Trychosis (p. 333) 



Prepectal carina reaching subtegular ridge (figs. 315,b and 316, a); nervulus 

 at or basad of basal vein; prepectus without a vertical carina opposite 

 lower corner of pronotum; epomia usually weak or absent 5 



5. Sides of areolet strongly convergent (fig. 315,b); notaulus sharp, reaching at 



least to center of mesoscutum; ovipositor tip rather abruptly tapered from 

 a distinct nodus; clypeua moderately small .... 15. Hidryta (p. 318) 

 Sides of areolet subparallel (fig. 316, a); notaulus absent or weak and short, 

 not reaching center of mesoscutum; ovipositor tip gradually tapered from 

 an indistinct nodus; clypeus large 16. Idiolispa (p. 322) 



