Subfamily Gelinae 



The Mesostenini, subject of this revision, is one of three tribes of 

 the subfamily GeUnae. Since the limits of the Mesostenini need 

 definition, we give below a characterization of the subfamily, then a 

 key to and descriptions of its tribes : 



Clypeus separated from face by a groove; male flagellum usually 

 with tyloids; areolet with the intercubiti nearly always separate on the 

 radial vein, nearly always pentagonal or quadi'angular, sometimes 

 open apically but the pentagonal or quadrangular shape usually still 

 indicated; wings sometimes vestigial or absent; apex of front tibia 

 rounded on outer side, without a small angle or tooth; sternaulus 

 usually sharp and longer than half the length of mesopleurum; tarsal 

 claws apparently simple; first abdominal tergite fused with its sternite, 

 without a lateral pit or groove in front of its spiracle, more or less de- 

 cm'ved at the spiracle and broadened beyond, the spiracle usually 

 beyond the middle but sometimes at or just in front of the middle; 

 abdomen nearly always depressed, its third segment being wider than 

 deep (compressed in females of Tropistes and of Atractodes) ; ovipositor 

 usually extending beyond apex of abdomen, its dorsal valve without a 

 preapical notch, or if a preapical notch is present this is on a subapical 

 elevation and the lower valve has an apical series of teeth. 



This is a distinct subfamily, but as indicated above most of its 

 characters are subject to some exceptions. The pentagonal or quad- 

 rangular areolet, long sharp sternaulus, depressed abdomen, ovipositor 

 surpassing apex of abdomen, spiracles of first abdominal segment be- 

 yond the middle, and tergite of first abdominal segment fused with its 

 sternite make a combination of characters that permit reliable recog- 

 nition, but all except the last of these characters is subject to ex- 

 ceptions. Probably the beginner will have most difficulty separating 

 the Gelinae from the Ichneumoninae, which like the Gelinae have a 

 pentagonal or sometimes quadrangular areolet, and further similarities 

 in the first abdominal segment and general shape of the body. The 

 Ichneumoninae differ from the Gelinae most conspicuously in having a 

 shorter weaker sternaulus, ovipositor not surpassing apex of abdomen, 

 and larger, flatter, and more truncate clypeus. Here, again, there are 

 exceptions to the differences, and experience or comparison material 

 will sometimes be necessary. No practical characterization to cover 

 all cases seems possible. The Ichneumoninae and Gelinae, though 

 sometimes hard for beginners to separate as adults, have larvae which 



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