192 NEW YORK STATE MUSEUM 



. ^ ee Basal joints black 



t Crossvein clouded with black or brown 

 g Fore metatarsus about 1^^ times its tibia in length; ante- 

 rior tarsi of both sexes very slender and without hairs or 



with but few hairs ; legs pale 20. riparius 



gg Fore metatarsus less than I14 times its tibia in length; 



anterior tarsi of the male bearded 



h The second fore tarsal joint shorter than the third ; male 



fore tarsi long and densely bearded. ...21. barbipes 



hh The second fore tarsal joint longer than the third; male 



fore tarsi long but thinly boarded. . . .22. annularis 



ft Crossvein not clouded 



g Length about 7 mm. ; black, abdomen black, in the male 

 sometimes with yellow latteral spots ; male fore tarsi 

 delicately bearded ; fore metatarsus about 1^ times the 



length of its tibia 23. d i s p a r . 



gg Length less than 6 mm. 



h Thorax shining black, not striped ; abdomen black 

 i Legs blackish, fore metatarsi white ; length 4 mm. 



24. albimanus 

 ii Legs pale yellow ; abdomen of female with paler base ; 



length 3.5 mm 25. t e n e 1 1 u s 



lili Thorax duller, with indications of black or grey stripes 

 i Abdomen either olive green, or black and white 



;■ With dark olive green abdomen; legs ferruginous; 



length 4.5 mm. ; male 26. c h 1 o r i s 



jj With white posterior margin on each abdominal seg- 

 ment ; legs black and white ; length 4 to 5 mm. 

 k Fore femora black, fore metatarsus less than 1.33 



times as long as its tibia 27. devinctus 



Tck Middle section of each femur, white; fore meta- 

 tarsus about 1.66 times its tibia in length 



28. c a 1 i f o r n i c u s n. sp. 

 ii Abdomen black 



j Thorax blackish with black stripes; legs wholly 

 white, except sometimes middle section of fore 

 femora is brownish (abdomen of male is white) ; 



female 32. nigricans n. sp. 



jj Thorax dark brown with broad yellowish median 

 vitta on anterior half and a pair of gray vittae on 

 posterior part ; abdomen velvet-black, hairs yellow 



(District of Columbia) 29. p a 1 1 i a t u s 



1)1) Thorax or abdomen or both with considerable green or yellow or gray 

 c Thorax entirely shining black, excepting sometimes the humerus, 

 which may be yellow 



d Abdomen yellow with brown bands ,1. b r a c h i a 1 i s 



dd Abdomen bright green, paler when dry, posterior segments darker 

 e Halteres wholly pale 30. p e d e 1 1 u s 



