WASP GENUS CERCERIS — SCULLEN 427 



Head subequal in width to the thorax; black except most of the 

 face, a small patch back of the eye, base of the mandible, and a patch 

 on the scape, all of which are yellow; clypeal border with four exten- 

 sions, the medial two in the form of roimded carina and the two 

 lateral ones denticle-like; the clypeal surface elevation broad, uni- 

 formally convex, and with a lamella on the free margin, the lamella 

 more or less emarginate but not divided; mandibles with three denti- 

 cles, the most apical one the largest and pointing apically; antennae 

 normal in form. 



Thorax black except for a divided band on the pronotum, two oval 

 patches on the scutellum, small spot on the pleuron, and spot on the 

 tegulae, all of which are yellow; tegulae low and smooth; enclosure 

 with a light medial groove and light ridges at about a 45° angle to the 

 base; mesosternal tubercle small; legs yellow to fulvous with a darker 

 area on the base of the femora and on the two basal segments. 



Abdomen with terga 1 and 6 immaculate, tergum 2 with a broad 

 band on the posterior half, terga 3, 4, and 5 with narrow bands 

 deeply emarginate; venter immaculate; pygidium oval with the apical 

 end the narrower. 



Male. — Length 10 to 11 mm. Black with yellow markings; 

 punctation average; pubescence short. 



Head subequal in width to the thorax; black except for the entire 

 face, basal half of mandibles, and the scape, all of which are yellow; 

 extension on the medial lobe of the clypeus narrow with three indis- 

 tinct denticles; clypeal surface convex; hair lobes very narrow, less 

 than the width of the lateral clypeal lobes; lateral clypeal lobes 

 covered with prominent setae; mandibles with one small acute medial 

 denticle; antennae with the apical segment slightly curved. 



Thorax black except for a divided band on the pronotum; a semi- 

 divided band on the scutellum, spot on the pleuron, and a spot on the 

 tegulae, all of which are yellow; tegulae low and smooth; enclosure 

 without the usual medial groove, somewhat punctate laterally and 

 lightly rugose along the anterior margin; mesosternal tubercle absent; 

 fore- and midlegs with the first two segments black and yellow, the 

 femora very dark basally, becoming light apically, remaining segments 

 yellow; hindlegs with the coxae black and yellow, trochanters yellow, 

 femora black basally, and the remaining segments largely amber with 

 darker areas; wings subhyaline but clouded. 



Abdomen with terga 1 and 7 immaculate, tergum 2 with a broad 

 band on the posterior half; terga 3 to 6 with narrow emarginate 

 bands; venter with traces of yellow laterally on sternites 2, 3, and 4; 

 pygidium with convex sides converging to a truncate apical end. 



Superficially, C. robertsonii robertsonii Fox closely resembles C. 

 clypeata Dahlbom, C. atramontensis Banks, and other related forms in 



