Fossorial Hi/men ojitera of North America. 415 



Trypoxylon frigidum, Smith. 



T. frigidum, Smith. Cat. Hym. Br. Mas. iv. p. 380. (1856). 

 % . Head black, very minutely punctured, not pubescent, except on 

 the clypeal region; clypeus with a dull mesial tooth; mandibles red- 

 dish externally; antennas not emargiuate; thorax very smooth and 

 shining, only pubescent on the flanks; propodeum unusually free from 

 pubescence, with a few slight irregular unequal striae at base, slightly 

 diverging from the mesial line, posteriorly very slightly rugose with 

 fine lines ; mesial line raised, distinct, posteriorly a long ovate pit, on 

 the flanks a slight longitudinal ridge ; tegulfe and nervures black. 

 Legs black throughout, tarsi concolorous, hind tibial spurs testaceous, 

 not sericeous. 



Abdomen thick, clavate, not much longer than the head and thorax 

 together, black, smooth and shining. 

 Length, .26 inch. 



9 . Differs in its broader, more transverse head, more clavate anten- 

 nas, longer acute abdomen, and the rugas on the propodeum are much 

 more distinct, there being a broad subtriangular enclosure, with about 

 five unequal rugae on each side of the mesial ridge, which is distinctly 

 demarked from the minutely lineated posterior surface of the propo- 

 deum. 



Length, .32 — .44 inch. 



Illinois, New York, (Coll. Ent. Soc. Phil). West Farms, N. Y., 

 (Angus). Connecticut, (Norton). "Cambridge, June 1 — 15, July 

 15, on flowers." Harris. Maine, (Harris). Dublin, N. H., Leonard, 

 (Harris Coll.). Brunswick, Me., July and August, (Packard). 



Easily recognized by its small size, the black head, with its silvery 

 pubescence which is confined to the orbits and clypeal region, as the 

 body generally is remarkably free from pubescence. The smooth tho- 

 rax and distinct propodeal area is rugose, and posteriorly lineated, in 

 which it differs from all the other species, as much as by the want of 

 the pubescence. The abdomen is unusually thick at the base, being 

 regularly clavate. 



It lives in the stems of Syringa, from which it has been reared by 

 Mr. Angus. 



Trypoxylon collinum. Smith. 



T. collinum, Smith, Cat. Hym. Br. Mas. iv. p. 381. (1856). 

 % . Front narrow, coarsely punctured, indentation of the eyes nar- 

 row and deep ; a black, prominent, undivided tubercle below the ocelli; 

 clypeal region thickly silvery pubescent; edge of clypeus bideutate ; 

 surface not much raised, no mesial carina ; mandibles pale red, palpi a 



