Fossorial Ilymenoptcra of North America. 359 



the joint itself, and twice as broad as long; outer margin brown beneath , 

 tibia; expanded into an unusually large, concavo-convex, sub-triangular 

 plate, longer than broad, five-sided, the anterior edge inrolled and sinuate, 

 thus making the anterior edge appear straight when seen from above ; 

 posterior edge deeply excised ; base of vexhilluui thinly covered with 

 yellow transparent dots, giving it a sieve-like appearance ; these disap- 

 pear on the outer edge, where it is deep brown : beneath, these holes 

 are arranged in sinuate lines over the tibial joint, no radiating lines on 

 the anterior half; basal joint of tarsus long and expanded triangularly; 

 mesial joints very short and broad, fused together, terminal joints hardly 

 expanded, larger, thin, and terminating in a flat triangular expansion ; 

 its edge broad, and abruptly terminating in a long, slender, incurved 

 hook. Middle and hind trochanters and femora black; tips of the 

 middle yellow ; inner side of the hind tibiae streaked with brown, ter- 

 minal joints of tarsi fuscous. 



Abdomen with sinuate yellow fasciae on the three basal segments, 

 the middle pair largest, nearly meeting on the median line of the body, 

 the third pair indented on their front edge ; a narrow, transverse, con- 

 tinuous band on the hind edge of 4th and 5th rings, dentated in front, a 

 pair of fasciae situated in the middle of the 6th ring, separated by a 

 triangular black space ; in middle of the 7th and terminal ring is a 

 single yellow dot, sometimes nearly obsolete. Beneath, as usual, 

 black. 



Length of the body, .42; head and thorax, .20; abdomen, .21 inch. 



Maine, common in August on Spiraea, (Packard), Mass., (Sanborn). 

 Illinois, (Coll. Ent. Soc. Phil.). 



Our most abundant species northwards, it can be easily recognized 

 by the larger vexhillum and peculiar tarsi, and want of any yellow spot 

 on the ciypeus, and by the dentated yellow lines on the terminal rings 

 of the abdomen. 



T. argus, Pack. 



Crabro argus, Harris, Cat. Ins. Mass. p. 68. (1835). 



% . Head shorter and narrowing behind more than in any other spe- 

 eies, front more deeply excavated, and thus the eyes and ocelli render- 

 ed more prominent, the vertex being unusually convex, front broader, 

 eyes more remote and clypeal region broader than in T. cribrellifer ; 

 surface puncto-striated, but more coarsely punctured and less finely lin- 

 eated than in T. cribrellifer. Orbits on anterior half of the front sil- 

 very pubescent; ciypeus yellow, covered with a dense silvery pubes- 

 cence ; mandibles yellow, tips corneous ; antennae with the scape dilated 

 and longer than in T. cribrellifer, entirely yellow ; flagellum remark- 



