262 U. S. NATIONAL MUSEUM BULLETIN 216 



Black. Face, rather small triangular spot at top of eye, cheek, 

 mouth parts, spot on front of scape, large hind corner of pronotum, 

 tegula, subtegular ridge, apex of scutellum, and postscutellum, pale 

 yellowish, the face of female with a median subdorsal vertical stripe 

 or elongate brown spot; flagellum dark brown beneath; front and 

 middle legs fulvous, their coxae apically (especially in male) and male 

 femora apically, paler fulvous or yellowish; hind coxa, trochanters, 

 and femur fulvous ; hind tibia fulvous, brownish at extreme base and 

 in male with a subbasal yellow tinge; hind tarsus fulvous stramineous, 

 the apex of first through fourth segments and fifth segment except 

 basally, fulvous. 



Type: 9, "River Heights," Utah, July 12, 1935, C. F. Smith 

 (Washington, USNM 63680). 



Paratypes: 9, Moscow Mt., Idaho, Aug. 4, 1936, Shull and Coon 

 (Washington). d\ near Glacier Point, Yosemite National Park, 

 Calif., July 19, 1948, H., M., G., D., and J. Townes (Townes). 



XI. MANDIBULARIS GROUP 



Front wing 3.7 to 7.0 mm. long; head rather broad, with full temple 

 and rather wide face that is weakly convex transversely and moder- 

 ately convex in profile; interantennal process of face broadly trian- 

 gular, not elongate; frons bulging just below the ocelli; cheek about 

 0.65 as long as basal width of mandible; occipital carina absent; 

 clypeal margin strongly convex or subangulate medially; mandible of 

 male normal for the genus, of female with a strong transverse sub- 

 basal groove, immediately apicad of which the mandible is strongly 

 inflated; face, more or less of side of frons, spot at top of eye (often 

 connected with frontal mark), lower part of temple, cheek, clypeus, 

 and mouth parts yellow to white, the face sometimes with a median 

 dark area; notaulus sharply impressed but very short; metapleurum 

 without discal setae; costula present or absent; second lateral area of 

 propodeum often with a very few hairs in its apicolateral corner, other- 

 wise bare; apical transverse carina of propodeum complete; nervulus 

 beyond the basal vein by about 0.6 its length; front spur of middle 

 tibia about 0.5 as long as hind spur; second segment of middle tarsus 

 about 1.5 as long as wide in male, about 1.2 as long as wide in female; 

 hind tibia yellow or whitish, usually fuscous at base and apex; first 

 tergite 1.55 to 2.5 as long as it is wide at basal corners; second tergite 

 about 0.7 to 1.2 as long as wide, with small sharp punctures, very 

 sparse medially, sublaterally with interspaces about 2.5 their diameter; 

 epipleurum of third tergite oblong, broad, with a broadly rounded 

 inner front corner. 



This group is a specialized offshoot of the tibialis group, distinguish- 

 able on the convex clypeal margin and the specialized mandible of 



