192 CHARLES ROBERTSON. 



3. Sides of face, front and cheeks with black bail-; abdomen shining; cell III5 



^1114 to vein IV2 carlini. 



Cheek behind summit of eye with some black hairs ; cell III5 about one-half 

 as long as III4 salicis. 



4. Cell III4 twice as long as III5 ; rather small species 7. 



Cell III4 not twice as long as III5 ; rather large species ; joint 3 = 5 5. 



5. Last ventral segment with a conspicuous tuft of long hair pruni. 



Last ventral segment without a conspicuous tuft of long hair 6. 



6. Cell III4 longer than III5 ; abdomen with rather long pale pubescence, subfas- 



ciate ; enclosure rather coarsely rugose sayi. 



Cell III4 and Ills subequal ; abdomen with short dark pubescence, not suh- 

 fasciate ; enclosure finely rugose viciniformis. 



7. Wing with conspicuous cloud at tip; joint 3 = 5; enclosure finely rugose at 



base ; apical ventral process truncate nubecula. 



Wing hyaline ; joint 3 sometimes no longer than 4 ; enclosure unusually rugose ; 

 apical ventral process emarginate nasonii. 



8. Apex of abdomen densely tufted ; enclosure quite broad ; scutel usually purplish ; 



slender apecies illinoensis. 



Apex of abdomen not densely tufted ; enclosure ordinary ; scutel without 

 purplish ; less slender species 9. 



9. Abdomen bluish ; vein IV3 arising before middle of cell III5 g-eranii. 



Abdomen greenish ; vein IV3 arising beyond middle of cell III5 ■ .polemonii. 



10. Cheek various, the angle opposite or below middle of eye 13. 



Cheek subtriangular, the angle above middle of eye 11. 



11. Mandibles simple at base ; joint 3 shorter than 4 4" 5; abdomen impunctate, 



segments with margins broad, testaceous, elsewhere more or less black 

 and greenish, or more or less red ; flagellum pale beneath 



erythrogastra. 



Mandibles toothed at base; angle of cheek strongly produced, compressed, 



sometimes a little carinate; pubescence of head without black ... -12. 



12. Joint 3 about = 5 mandibularis. 



Joint 3 about = 4 + 5 tridens sp. nov. 



13. Cheek subtriangular, angle opposite middle of eye; joint 3 almost as long as 



4+5; abdomen greenish erythronii. 



Cheek broad, subquadrate, border carinate; angle below middle of eye; cly- 

 peus strongly produced, reflesed, widely emarginate • • • -platyparia. 



PTIL<4iWDRE!VA gn. nov. (Type Andrena erigenix Eob.). 



FEMALES. 



Hind tibia as long as the tarsus; fovea narrow ; joint 3 nearly =4-6. 



Fovea not reaching below antenna; process short, broad ; abdomen opake, rather 

 strongly, sparsely punctured erlg-eniae. 



Fovea reaching below antenna ; process triangular, truncate or emarginate ; ab- 

 domen shining, impunctate, or nearly g-. maculati. 



MALES. 



Angle of cheek above middle of eye; joint 4 shorter than 5; abdomen punctate, 

 angles of ventral segment 6 somewhat reflexed, apical ventral process 

 strongly and sharply furcate erig-eniee. 



Angle of cheek below middle of eye; joints 4 and 5 subequal ; abdomen almost 

 impunctate g. maculati. 



