ICHNEUMON-FLIES — GELINAE : MESOSTENINI 7 



A revisionary study of the tribe would add some new genera, proba- 

 bly synonymize a few, and subdivide the genus Cubocephalus. 



The genera Hemigaster and Mansa have some characters in common 

 with the subtribe Baryceratina, tribe Mesostenini. These resem- 

 blances may be due either to close relationship or to convergence. 

 The evidence in support of either possibility is inconclusive. 



3. Tribe Mesostenini 



Front wing normally 3.5 to 27 mm. long (wings I'urely vestigial); 

 apex of clypeus various; areolet present or absent; second recurrent 

 vein with one bulla, vertical or sloping inward slightly so that outer 

 hind corner of second discoidal cell is a right or obtuse angle and 

 is not longer or sharper than outer front corner, or rarely the second 

 recurrent vein slopes outward (as in Bozakites and related genera); 

 dorsal rim of metanotum entire, without a sublateral tooth or angle 

 (except in some species of Echthrus), though a sublateral tooth or 

 angle is sometimes present just below this dorsal rim; propodeum 

 usually with only the two transverse carinae, the basal carina usually 

 stronger and more persistent than the apical carina, often the median 

 basal area and rarely additional areas defined by carinae. 



This tribe has frequently been divided into two: the "Cryptini" 

 with the areolet large and the Mesostenini with the areolet small. 

 Such a division is quite artificial, as it separates closely related genera 

 and groups together genera which are unrelated. Moreover, the 

 size of the areolet is often intermediate, which makes the character 

 impractical in application. The two tribes as divided formerly 

 should be combined, and certain subtribes, based on more natural 

 characters, made for the better handling of this very large group of 

 genera. An attempt at sub tribal divisions is made below. It seems 

 probable that the Mesostenina, the largest subtribe, should be sub- 

 divided further. Future studies may point the best way to accom- 

 plish this. 



Biology 



The biology of the Mesostenini is in general like that of the rest 

 of the Gelinae. Typically, the subfamily is parasitic in cocoons, 

 usually lepidopterous cocoons but also cocoons of sawflies, of braconids 

 and ichneumonids, of Neuroptera, of Gyrinidae, egg cocoons of spiders, 

 puparia of Diptera, and nests of wasps. Some genera are parasitic on 

 pupae in stems, and a few have gone beyond this habit to attack 

 borers in wood. Females locate hosts pimarily by searching on foot, 

 exploring with their antennae. Correlated with this habit the an- 

 tennae of females are flexible, have a sensory area on the under side of 



