PROC. EXT. SOC. WASH., VOL. 21, NO. 5, MAY, 1919 11.'! 







Genus Derocentrus, new genus. 



* 



Runs in Ashmead's key to Nematopodius and is probably what 

 he used in the construction of his key to the Mesostcnini; but is 

 conspicuously different from the genotype, Nematopodius for- 

 mosns Gravenhorst. The ovipositor is much longer than the 

 body; the first tergite not parallel-sided, but has the postpetiole 

 much broader and higher than the petiole and the spiracle much 

 behind the middle; and the other tergites broad, not long and 

 narrow. Also the antennal annulus embraces flagellar joints 

 6-9, not 15-16 as in formosus; the front coxae normal, without 

 a transverse ridge on the outside; the pronotum short medially; 

 the propodeum not extending beyond the base of the coxae, the 

 basal carina strongly angulate medially; the second joint of hind 

 trochanters nearly twice as long as first joint. In all the species 

 referable here the entire insect is without contrastingly colored 

 maculation except more or less blackish stains principally in the 

 alar region, and the head and thorax are sculptured. 



The following generic description is based entirely on the 

 female, the male being unknown. 



Slender, with legs and antennae long and slender, abdomen clavate, ovi- 

 positor much longer than body. Head transverse; temples strongly convex, 

 much narrower than eyes; frons deeply concave ; eyes large, subparallel within; 

 face with oblique impression each side of middle; clypeus broad, convex, 

 broadly subtruncate; labrum exserted; teeth of mandibles of equal length; 

 malar space nearly as long as basal width of mandible; thorax shining, punc- 

 tured; notauli deep, meeting on disk of mesoscutum; propodeum subconcave 

 behind, basal carina strong, strongly angulate medially; basal area small 

 quadrate; apical carina distinct laterally, obsolete to wanting medially as 

 is also that portion of median longitudinal carina lying between the trans- 

 verse carinae; wings long, stigma narrow lanceolate; areolet very small, 

 much longer than wide, second intercubitus incomplete; second recurrent 

 slightly antefurcal with respect to the second intercubitus; legs very slender; 

 hind trochanters half as long as femur, second joint cylindrical and nearly 

 twice as long as first ; basitarsus as long as other joints combined, apical joint 

 shorter than third ; abdomen long, clavate, polished; first tergite completely 

 fused with sternite, spiracles at apical two-fifths; postpetiole slightly wider 

 than petiole; second tergite subsequal in length to first, constricted at base, 

 much wider at apex; other tergites barely half as long as second, broader than 

 long; ovipositor nearly or quite twice as long as body; lanceolate at apex. 



Uniform ferruginous with more or less black in alar region, antennae black, 

 ferruginous at base, with an incomplete white annulus embracing more or 

 less of flagellar joints 6-9; wings suffused with brownish. 



Type. (( 'olcoccntrns) Xcmatopoilins ic\\iuus (Ashmead). 



