218 Wisconsin Academy of Sciences, Arts, and Letters. 
15. Abdomen with only four visible segments, very convex, the 
venter excavated; first two joints of the antennae very 
short, the third large, subquadrate, with a short subtermi¬ 
nal arista.*iNausigaster 
Abdomen with more than four visible segments. 
16. iHind femora distinctly thickened. 
Hind femora but little or not at all thickened. 
17. Scutellum unusually large, nearly square; males dichoptic_ 
. *Chalcomyia 
Scutellum not unusually holoptic, with facial tubercule. 
.... *Myiolepta 
18. Face rounded, not tuberculate, the oral margin not pro¬ 
jecting ... Fipiza (p. 224) 
Face tuberculate or the oral margin projecting. 
19. Epistoma projecting; small, black species... 
Face tuberculate, the oral margin not projecting. 
20. Front in the female and usually the face in both sexes with 
transverse wrinkles; spurious vein obsolete; antennae 
short or long.. Chrysogaster (p. 223) 
Front and face not wrinkled; face pilose.*Psilota 
21. Metallic green, metallic green and black, or black species; facial 
orbits separated by a slender parallel grove . 
...Chilosia (p. 226) 
Black with more or less metallic green or blue, with yellow, 
yellowish, or metallic cross-bands on the abdomen; face not 
with orbital grooves .. 
22. Face with transverse grooves in the middle; antennae elon¬ 
gate .*iRhysops 
Face not with transverse grooves or wrinkles... 
23. Wings not longer than the abdomen; ocellar tubercle large; 
abdomen depressed, long elliptical, somewhat narrowed to¬ 
ward its base, the markings ferruginous or orange yel¬ 
low .. Pyrophaena (p. 228) 
Wings longer than the abdomen, abdomen with yellow or 
greenish-yellow, or shining metallic cross-bands; usually 
elongate species . 
24. Front tibiae distally and the tarsi of the male dilated, those of 
the female slightly widened. platycheirtjs (p. 229) 
Front tibiae and tarsi slender in both sexes.. 
25. Rather large, blackish species, with a large flat, elliptical ab¬ 
domen .*Xanthandrus Verrall 
More elongate and slender species; abdomen not elliptical in 
outline. Melanostoma (p. 231) 
26. Abdomen narrowed toward the base, distinctly club-shaped or 
spatulate in outline .... 
Abdomen oval or slender, not spatulate or club-shaped in out¬ 
line ... 
27. Third longitudinal vein bent deeply into the first posterior 
cell . *Salpingogaster 
Third longitudinal vein straight or gently curved. 
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