AKT. 16 NORTH AMERICAN ICHNEUMON-FLIES — CUSHMAN 43 



don, August 21-28, 1912, ex Phlyctaenia extricalis, J. F. Strauss, four 

 females, four males. Alabama — Pyziton, one female, one male, 

 Lanp^clale, one male, H. H. Smith. Louisiana — one female (Baker 

 collection) ; Lake Charles, November 13, J. C. Crawford. Missouri — 

 Kirkwood, ex Neplwpteryx pergratieUa^ November 11, 1882, Mary 

 E. Murtfeldt, one female. Arkansas — Bentonville, ex Mineola, June 

 21, Quaintance No. 20733, one male; July 18, one male, D. Isely. 

 Texas — Dallas, May 23, 1906, F. C. Bishopp, one male. Kansas — 

 Ona«»;a, Crevecouer, one male; Lawrence, August 20, 1896. Hugo 

 Kahl. Colorado — one male, determined by Cresson. 



MESOSTENUS GRACILIS Cresson 



Mesostenus ffracUis Cresson, Proc. Ent. Soc. Phila., vol. 3, 1864, p. 315, male. 



Type.— No. 1180, Acad. Nat. Sci. Phila. 

 Nematopodius orhitaUti Ashme^vo, Bull. Colo. Biol. Assn., vol. 1, 1890, p. 21, 



female. Type. — Cat. No. 24081, U.SN.M. (new synonymy). 

 Mesostenus gracilis (Cresson) Vib3{eck, Smith: Insects of N. J., 1910, p. 630. 



Discussion based on type, that of orbitalis and 20 other males and 

 30 other females in the National collection. 



The type of orhitalis is in very bad condition with abdomen and 

 many of the appendages missing, but I have no doubt of the cor- 

 rectness of the synonymy. 



Female. — Length (>-12 mm. 



Not at all like NematopodivrS., to which genus Ashmead referred it, 

 but a typical Mesosterms very closely allied to tJioracicus Cresson, 

 from which it differs as follows: 



More slender, the thorax hardly half as deep as long; temples 

 distinctly convex; malar space nearly as long as basal width of 

 mandible; mesopleural impressions not at all striate; apical carina 

 of propodeum broadly interrupted medially, not high on angles, 

 abdomen fully a half longer than head and thorax; second tergite 

 fully twice as long as broad at base ; sheath not or barely two-thirds 

 as long as abdomen; ovipositor much more slender, especially at 

 apex; orbits usually continuously white, rarely interrupted at top 

 of eyes behind; mesoscutum frequently largely reddish, with only 

 the notauli and sutures black ; front and middle coxae at most partly 

 white, rarely partly black; hind tarsus usually entirely red, rarely 

 with joints 2-4 whitish. 



Male. — Differe from male of thoracicus as follows: 



Temples strongly convex; propodeum finel}^ rugose behind, apical 

 carina usually entire, but sometimes interrupted medially, not espe- 

 cially higher on angles; antennae usually without annulus, rarely 

 with a distinct annulus; hind tarsus with at most joints 2-4 white, 

 frequently entirely black or blackish; hind coxa entirely red. 



