78 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



Supraclypeal area flat, somewhat elevated adjacent to the 

 median fovea; body black, with front and middle legs below 

 knees, basal half of posterior tibiae, and metatarsi, white; 

 pentagonal area rounded in outline behind, walls low and 

 fading out before; median fovea shaped like an impressed 

 tetrahedron with all its margins broadly rounded; saw- 

 guides retracted, convex below and bluntly rounded to a 

 blunt point; wings infuscated on basal half. Length 6 mm. 



lorata 



5. Postocellar area distinctly broader than long and not strongly 



convex; body black, with front and middle legs below 

 knees, hind legs with knees, basal half of tibiae, and tarsi 

 more or less, white; pentagonal area angular in outline 

 behind median ocellus, with distinct walls, gradually fad- 

 ing out in front; median fovea shaped like an impressed 

 tetrahedron, the outer margin being rounded; saw-guides 

 convex above and below, gradually rounded to a point at 



the apex; wings hyaline. Length 4.5 mm lunata 



Postocellar area about as long as broad and strongly 

 convex; body black, with front and middle legs below 

 knees, basal two-thirds of hind tibiae, and basal three- 

 fourths . of hind metatarsi, white or luteous; pentagonal 

 area angular behind median ocellus, deep and distinctly im- 

 pressed, walls slanting; median fovea deep and strongly 

 impressed, sides parallel, gradually shelving off above; 

 front with deep, round, pit-like lateral fovese not joining 

 the antennal foveae; saw-guides straight above, broadly 

 convexly rounded below to a blunt point at apex above. 

 Length 4-6 mm quercus-alba 



6. Front with sides of pentagonal area extending ridge-like 



to bases of antennae, never mound-like 7 



Front with sides of pentagonal area expanded above bases 

 of antennae into mound-like elevations; body black, with 

 front and middle legs below knees, hind tibiae on basal 

 half, and their tarsi in part, white; pentagonal area with 

 all its walls perfectly flat; clypeus deeply emarginate; saw- 

 guides retracted, pointed at apex; wings hyaline. Length 

 5-5 mm lobata 



7. Frontal crest strongly elevated above general level of basin 



above it; walls of pentagonal area distinct, strongly ex- 

 panded below into a pair of elevated parenthesis-shaped 

 ridges; body black, with legs below knees, except 

 apical half of posterior tibiae, white; antennae with third 

 segment subequal in length to fourth and fifth together; 

 saw-guides with sides parallel, slender, and bluntly 

 rounded at apex; wings infuscated on the basal half. 

 Length 6 mm obsoleta 



