NORTH AMERICAN IIYMENOPTERA. 145 



13. Crabro nigrifrons Cress. 



Crabro adveiia (in part) Smith, Cat. Hym. Brit. Mus., iv, 421, % {mm 9)- 

 Crabro nigrifrons Cresson, Proc. Ent. Soc. Phila., iv, 482, % . 

 Crabro contigiiiis Cresson, ibid. p. 484, 5 

 9. — Head finely and closely punctured; first joint of flagelluni scarcely as 

 long as the three following ones united ; frontal impressed line distinct ; dorsulum 

 and scutellum finely and closely striato-punctate ; mesopleurse very finely and 

 closely striated, rather suhtilely so; middle segment above with not very strong 

 longitudinal striations, the central furrow long and narrow, upper surface not 

 separated from posterior face by fovese, posterior face delicately and transversely 

 striated, without any trace of lateral ridges, sides delicately striated. Black ; 

 large spot on mandibles, scape entirely, pedicellum in part, two variable S])ots on 

 pronotum, tubei'cles. spot on scutellum and metanotum sometimes, although these 

 parts usually not spotted, tips of fore and medial femora more or less, and tips of 

 hind pair sometimes, tibite except a dark spot internally, tarsi except a])ical joints 

 and a long narrow spot on each side of dorsal abdominal segments 2-4, those on 

 segment 4 united, yellow; the abdominal spots in rare cases, all united in bands, 

 or nearly so, in which event the sjjots are broader and the first segment spotted ; 

 tegulfe entirely testaceous. Length 11-12 mm. 



% . — First four joints of flagellum armed with a large tooth beneath, the com- 

 bined length of the first two joints not greater than the length of the following 

 three joints united ; dorsulum more strongly sculptured than in the 9 . appearing 

 granulated anteriorly ; middle segment with the sculpture coarser than in the 

 other sex, central furrow broader, and the upper and posterior faces separated by 

 fovese, posterior face rather coarsely and transversely striated, and with poorly 

 developed lateral ridges, sides not so coarsely striated as the posterior face ; first 

 joint of medial tarsi more strongly toothed or spined internally than in obsciiras 

 and (jracilissimus. Black, including the mandibles ; scape with a black spot poste- 

 riorly ; thorax marked as in the 9 I fore femora and tibiie in front and the me- 

 dial femora in part, rufous, the femora (except the hind pair) otherwise black 

 and yellow ; medial and hind tibiae yellow externally, black within ; flagellum 

 beneath, tegulse entirely and tarsi, except anteriors, testaceous ; abdominal spots 

 as in the 9 - t»ut of course an additional paii', and the first segment spotted. 

 Length 9-11 mm. 



Occurs from Canada to New York, westward to California and 

 Washington ; Colorado ; Nevada. The 9 specimens having the 

 abdominal spots united into bands have a yellow spot on the epister- 

 uum mesopleuralis, not evident in the other forms ; they are from 

 California and Nevada. 



4. Group sexmaculatus. 



The three species contained in this group differ from all those pre- 

 ceding by the medial portion of clypeus being rounded anteriorly, 

 and not produced into a truncated process ; abdomen indistinctly 

 punctured or impunctate ; pygidium with a lateral fringe of loug, 

 thick hair ; mesopleune rather coarsely striato-punctate ; flagellum 



TRANS. AM. ENT. SOC. XXII. (19) JUNE, 1895. 



