no. 1812. NEW ICHNEUMON FLIES— VIERECK. 179 



frontal basin , clypeus rather smooth compared with the face, covered 

 with shallow pits, its anterior edge truncate, the truncature about as 

 wide as the anterior edge adjoining, mandibles mostly castaneous, 

 palpi mostly fuscous; thorax black, mostly reticulate all over; pro- 

 podeum rounded off, coarsely reticulate, the lateral spines represented 

 by a kind of arcuate buttress, base of propodeum with a median 

 longitudinal carina extending from the base of the superior aspect to' 

 the beginning of the posterior aspect and flanked on either side by a 

 carina that attains the apex toward which it converges though nearly 

 parallel to its fellow of the opposite side, wings transparent fuscous 

 except proximad to the base of the stigma where the membrane is 

 nearly colorless and the veins mostly stramineous, distad to the 

 base of the stigma the veins are mostly fuscous like the stigma, coxaa 

 and proximal hind trochanters mostly black, rest of trochanters 

 mostly ferruginous like all the femora, hind tibiae ferruginous except a 

 fuscous stain at base and an apical blackish band enveloping the 

 apical third, remaining tibiae ferruginous; abdomen black with little 

 more than its basal third ferruginous, the ferruginous color of its base 

 extending laterally to a little beyond the middle, the corresponding 

 ventral area castaneous, the paired carinae of the base of the abdomen 

 extending nearly to the middle of the ferruginous area where they 

 become lost among the numerous longitudinal reticulo-striations 

 which continue to near the apical concavity where they are replaced 

 by a kind of reticulation mixed with rugosities, the end of the carapace 

 somewhat truncated and with a vague longitudinal sulcus down its 

 middle; pubescence generally distributed, almost imperceptible, 

 whitish or pale ochreous; tarsi fuscous or blackish almost throughout. 



Male. — About as long as the female, differing chiefly as follows: 

 Antennae 33-jointed, carapace not so markedly vaulted, propodeal 

 carinae and basal carina? of carapace indistinctly defined, hind tibiae 

 ferruginous throughout at base, apex of carapace rounded off, not at 

 all parted by a fissure transversely or by a vague sulcus longitudinally, 

 basal two-thirds of carapace mostly ferruginous, the remaining por- 

 tion mostly black; facial carina indistinct or wanting. 



Type.— Cat. No. 13487, U.S.N.M. 



Type-locality. — Four Mile Run, Virginia. 



Three specimens, two females and one male, collected May 30, 

 1910, by Frederick Knab, for whom the species is named. 



In many particulars this species agrees with Chelonus laticinctus 

 Cresson, of which I had the type for comparison. Of the British 

 species it has characters in common with Chelonus wesmaelii Curtis. 

 From each of these, however, it differs abundantly, as may be gleaned 

 from perusing the above description. 



The female paratopotype is essentially like the type female, though 

 wanting the basal stain to the hind tibiae. 



