8 BULLETIN 834, U. S. DEPARTMENT OE AGRICULTURE, 



Trachelus tabid us Jurine (17). — Curtis (22). — Konow (41), (42). — Rudcw 

 (43).— Kokujev (44).— MacGillivray (45).— KHolodkovsky (46).— 

 Kulagin (47). — Kurdjumov (48). — Shtchegolev (49). — Uvarov (50).— 

 Borodin (52). — Zolotarevsky (53). — Uvarov and Glazunov (54). — Mac- 

 Gillivray (55). — Howard (56). 



Cephus nigritus Lepeletier (20). 



Cephus vittatus Costa (32). 



Calamenta johnsoni Ashmead (39). 



Calameiita johnsoni Ashmead (40). 



Cephus pygmaeus Cory (51), not Linnaeus. 



ADULT. 



Female. — Long and slender, with abdomen somewhat compressed. Antennae 

 longer than thorax, thickened at apex, third joint slightly shorter than fourth, 

 third to eighth joints four to five times as long as thick, those beyond eighth 

 gradually shortening, the ones in thickened portion of antennae subequal and 

 not longer than broad ; clypeus truncate at apex, with sharp lateral angles ; 

 occiput concave ; greatest width of posterior orbit about equal to greatest trans- 

 verse diameter of eye ; pronotum elongate, nearly as long as broad, broadest 

 at posterior margin, its sides more or less concave; mesoscutum and scutellum 

 subequal in length ; middle and hind tibiae each with two apical spurs and 

 normally each with two (sometimes one only) superapical spurs located at 

 about the apical one-third of tibiae; abdomen much longer than head and 

 thorax, subcompressed, with sheaths broad and slightly thickened at apex. 

 Polished black; mandibles except at apex, small spot below tegulse, apex of 

 front femora within, inner side of front tibiae for its whole length, spot at 

 apex of median femora in front, a broad longitudinal stripe along lateral 

 margins of dorsal segments, a lateral spot on seventh ventral segment, and a 

 narrow marginal stripe on basal part of sheaths yellow; wings subhyaline, 

 nervures and stigma black. (See PI. II, A.) 



Male. — Similar to female in general appearance and color. Last visible 

 ventral segment of abdomen prominent and extending beyond last dorsal seg- 

 ment ; two ventral segments before last visible segment each with a broad, 

 deep, horseshoe-shaped depression, within which is a transverse row of stiff, 

 erect bristles. (See PI. II, B.) 



The only species occurring in America, so far as known, with 

 which this species is likely to be confused are Cephus cinctus Norton 

 and Cephus pygmaeus Linnaeus. The female may be readily dis- 

 tinguished by the fact that in both cinctus and pygmaeus the sheaths 

 are narrower at apex than in the middle, and the dorsal segments 

 are banded apically with yellow. The legs are also more largely 

 yellowish. The male of tabidus differs from the males of the other 

 two species in the presence of the horseshoe-shaped depression on 

 the two ventral segments as well as by the color characters pointed 

 out for the female. 



OVERWINTERING LARVA. 



Body subcylindrical, yellowish white in color, 7 to 9 mm. in length, thoracic 

 region slightly thicker than abdominal region. Living larvae more or less tinged 

 with greenish due to body contents. 



Head pale yellow, its dorso-ventral length 1.1 mm., breadth 1.1 mm. Anten- 

 na? 5-jointed, tapering to a point at apex, more or less fuscous in color. Man- 

 dibles four-toothed, brownish, their apices nearly black ; labrum, sutures about 



