48 PROCEEDINGS OF THE NATIONAL MUSEUM vol.74 



Black, postpetiole, second tergite and base of third dark fer- 

 ruginous; antenna without annulus, legs black, more or less dis- 

 tinctly reddish beyond femora; wings infumate, front wing darker. 



Type-locality. — Calgary, Alberta. 



Type.— C^t. No. 40591, U.S.N.M. 



One female captured May 12, 1923 by George Salt. 



Genus DEROCENTRUS Cushman 



Derocentrus Cushman, Proc. Eut. Soc. Wash., vol. 21, 1919, p. 113. Genotype. — 

 (Coleocentrus texamis Ashmead) =Mesostenns madlentus Cresson. 



Very close allied to MesosteTms, but immediately separable by the 

 very long apical joint of hind trochanter and in female by the very 

 long ovipositor. 



The antennae in female and the legs are excessively slender ; the first 

 tergite is straight; the second tergite is very nearly as long as the 

 first and fully four times as long as broad at base, just behind which 

 it is slightly constricted ; the front tarsus is twice, and its basal joint 

 nearly, as long as tibia; the apical joint of the hind trochanter is 

 about twice as long as the basal joint and nearly half as long as the 

 femur ; the areolet is more elongate, the ovipositor is nearly or quite 

 twice as long as the body. Otherwise agrees well with the foregoing 

 description of Mesostenus. 



Only one species, having several synonyms, is thus far known. 



DEROCENTRUS MACILENTUS (Cresson) (new combination) 

 Figs. SflT, 4o, Ql 



Mesostenus longicaudis Cresson, Trans. Amer. Ent. Soc, vol. 4, 1872, p. 164, 

 female. (Not BruUe). Type.—Qat. No. 1578, U.S.N.M. 



Uesostenus macileiitus Cresson, Can. Ent., vol. 10, 1878, p. 210, male. Type. — 

 No. 1183, Acad. Nat. Sci. Phila. 



Mesostenus graciUpes, Cresson, Proc. Acad. Nat. Sci. Phila., 1878, p. 365, fe- 

 male. Type. — No. 1179, Acad. Nat. Sci. Phila. 



Coleocentrus texamis Ashmead, Proc. U. S. Nat. Mus., vol. 12, 1890, p. 444, fe- 

 male. Type— Probably Cat. No. 1578, U.S.N.M. Paratype.— Cat. No. 

 2105, U.S.N.M. 



Mesostenus macrurus Dalla Torre, Cat. Hym., 1901-1902, p. 544. 



Nematopodius longicatidus (Cresson) Ashmead, Proc. Wash. Acad. Sci., vol. 

 4, 1902, p. 206, female not male, 



Nematopodius exclamans Viereck, Trans. Kans. Acad. Sci., vol. 19, 1904, p. 

 318, female. Type. — Kansas University. 



Nematopodius graciUpes (Cresson) Viereck, Trans. Kans. Ac^d. Sci., vol. 19, 

 1904, p. 318. 



Nematopodius longicaudus (Cresson) Viereck, Trans. Kans. Acad. Sci., voL 

 19, 1904, p. 318. 



Nematopodius macilcntus (Cresson) Viereck, Trans. Kans Acad. Sci., vol. 19, 

 1904, p. 319. 



