434 U. S. NATIONAL MUSEUM BULLETIN 2 1 6 part 3 



and middle legs beyond trochanters fulvous, their fii-st trochanters 

 varied with whitish and fifth tarsal segments brown; hind first tro- 

 chanter fulvous and white, infuscate basally; second hind trochanter, 

 hind femur, and hind tibia, fulvous; fii"st segment of hind tarsus and 

 base of second segment fulvous bro^vn; fifth segment of hind tarsus 

 fulvous; remainder of hind tarsus white. 



Specimens: 9, Comstock, Tex., May 11, 1936, M. E. Chance 

 (Townes). cf , 9, Del Rio, Tex., Apr. 26 and 27, 1959, J. F. McAlpine 

 (Ottawa). 



28. Genus Mesostenus 



Figure 322,a 



Mesostenus Gravenhorst, 1829, Ichneumonologia europaea, vol. 2, p. 750. Type: 



Mesostenus transfuga Gravenhorst; designated by Westwood, 1840. 

 Sienaraeus Thomson, 1896, Opuscula entomologica, fasc. 21, p. 2380. Type: 



Mesostenus transfuga Gravenhorst; designated by Viereck, 1914. 

 Umlima Cameron, 1902, Ann. Mag. Nat. Hist., ser. 7, vol. 9. p. 208. Type: 



Umlima penetralis Cameron: monobasic. 

 Derocentrus Cushman, 1919, Proc. Ent. Soc. Washington, vol. 21, p. 113. Type: 



(Coleocentrus texanus Ashmead) = longicaudis (Cresson) ; original designation 



Front wing 2.7 to 9.3 mm. long; body slender; frons unarmed but 

 often with a median longitudinal carina that may be elevated as a 

 crest; clypeus of medium size, short, strongly convex, its apical 

 margin broadly truncate or weakly convex, without a median point; 

 mesoscutum strongly convex, polished or subpolished, its punctm-es 

 strong, rather close; notaulus sharp, extending beyond middle of 

 mesoscutum; epomia m.oderately strong; propodeum in profile rather 

 wealdy convex, its basal carina complete, its apical carina complete 

 or interrupted medially, forming weak, oblique, sublateral crests; 

 propodeal spiracle long, elliptic; areolet very small, quadrangular, a 

 little higher at apex than at base, about 1.6 as wide as high except in 

 M. eisenii, in which it is approximately square; ramellus absent; 

 nervulus basad of basal vein, usually by about 0.25 its length; base 

 of second discoidal cell broad ; mxediella rather weakly arched ; nervellus 

 broken below the middle; axillus close to anal margin; first abdominal 

 segment moderately long, rather slender, with a basal sublateral 

 tooth, its spiracle near its apical 0.39, its ventrolateral carina usually'' 

 distinct, its dorsolateral and median longitudinal carinae lacking; 

 second tergite polished or subpolished, its punctures of moderate 

 size, rather sharp, rather dense to quite sparse; tergite 7 without a 

 white spot; ovipositor sheath 0.57 to 3.5 as long as front wing, usually 

 about 0.73 as long; ovipositor moderately slender, somewhat com- 

 pressed, its tip rather slender. 



Mesostenus is a moderate-sized but widely distributed genus. It 

 is divisible into several species groups, of which two occur in our 



