ART. 16 NORTH AMERICAN ICHNEUMON-FLIES — CUSHMAN 9 



a deep depression at about the posterior third of the mesoscutum ; 

 seutelhim convex, not margined; sternauli deep, complete; propodeum 

 rather long, with the basal carina strong and nearly straight and 

 apical carina absent or slightly indicated laterally, without longitudi- 

 nal carinae, basad of basal carina polished, strongly transversely 

 striate beyond, spiracles elongate; legs slender, hind coxae large, 

 front tibia in female slightly inflated and weakly constricted basally, 

 hind tibia not nearly a half longer than femur, longer calcarium 

 reaching far beyond middle of basitarsus, tarsus subequal in length 

 to tibia, apical joint in female hardly as long as third, in male little 

 longer than fourth ; fourth joint of all tarsi, especially in female and 

 especially on front tarsus prolonged on outer side below ; stigma very 

 narroAv, radius slightly before middle; discoidal cell not conspicu- 

 ously narrowed at base; areolet small, pentagonal, about as long as 

 liigh, intercubiti parallel or nearly, second intercubitus obsolete, re- 

 current at or beyond middle; nervulus distinctly antef ureal, perpen- 

 dicular to medius or slightly inclivous; nervellus sharply broken, 

 strongly reclivous, upper abscissa perpendicular to mediella ; ab- 

 domen in both sexes broadest distinctly beyond middle, first segment 

 slender, decurved, spiracles at or very near the middle ; apical tergites 

 in female not conspicuously long; ovipositor sheath shorter than 

 abdomen, ovipositor slender cylindrical. 



Genotype. — Mesostenus discoidalis Cresson. 



The four North American species known to me are distinguishable 

 by the following key: 



1. Clypeus not apically inflexed ; antennae not at all compressed apically ; pro- 



podeum with lateral traces of apical carinae; subdiscoideus below upper 



third of postnervulus 2 



Clypeus apically inflexed ; antennae apically compressed, more strongly so in 

 female; propodeum without trace of apical carina; subdiscoideus at or 

 above upper third of postnervulus 3 



2. Abdomen with alternate bands of black and white discoidalis (Cresson). 



Abdomen red, bases of segments usually more or less darker, first segment 



whitish at base and apex rufiventris, new species. 



3. Eyes distinctly convergent below compressicornis, new species. 



Eyes hardly convergent below major, new species. 



MESSATOPORUS DISCOIDALIS (Cresson) (new combination) 

 Figs. 2&, 3c, 66, 8. 



Mesostenus discoidalis Cees.son, Trans. Amer. Ent. Soc, vol. 4, 1872, p. 162. 

 female. Type— Cat. No. 1575, U.S.N.M. 



Mesostenus jocosiis Provanciier, Nat. Can., vol. 6, 1874, p. 300. female; Nat. 

 Can., vol. 11, 1870. p. 112. female; Faune Ent. Can. Hymn., 1883. p. 346, 

 female. Type. — Public Mus. Quebec (new synonymy). 



Discussion based on type and 10 other females and 8 males, all in 

 the National collection. 

 Length, 8-9 mm. 

 5927—29 2 



