54 NORTH AMERICAN DIPTERA. 



food is wholly consumed. Frequently the larvae are found 

 free in the earth, however, where their transformation takes 

 place. The eggs are laid about grass stems, or in the crevices 

 of decaying trees infested by larvae of other insects. 



TABLE OF GENERA. 



1. Marginal cell of wings open. ....... 2 



Marginal cell closed. ......... 'P> 



2. Third joint of antennas with an arista or aristiform style ; abdomen 



slender; i)ulvilli wanting. . . . Leptogaster Meigen. 



Antenna^ not with an arista; usually with a thickened style. 



DaSYPOGONIN/E. 



3. Antennas witli a terminal bristle. ..... Asilix.^. 



Antenna? not witli a terminal bristle. .... Laphrin.ic. 



DASYPOGONIN^i:. 

 1. Front tibia? with a terminal, claw-like spur. .... 28 



Front tibiffi not with a terminal, claw-like spur. .... 2 



\^.A^ %2. Pulvilli rudimentary or wanting. . . . Ablautus Loew. 



.f..vwt-^ {jTV Pulvilli normal 3 



(jf Ak^. ■^- Ilcti^^ narrow, about as high as broad ; face narrow above, broader and 



/x,^,^^, swollen below, in large part covered with hair; large, elongate 



species. ........... 4 



Head very obviously broader than high. ..... G 



4. Antenna? with a terminal style 5 



Third joint of antennje long, without style; fourth posterior cell closed 



before the border of the wing; black species, with or without red on 

 the abdomen. Ospriocerus Loew. 



5. Style about half the length of tlie third antcnnal joint. 



SCLEROPOGON LoCW 



Style al)out a sixtli or an eighth of the length of the elongated third 

 joint. ........ Stenopogon Loew. 



0. Fourth posterior cell closed before the border of the wing. . 7 



Fourth posterior cell wide open, rarely nearly closed. . . .13 



7. Antenna^ much elongate, apparently composed of five joints. . 14 

 Antennie not elongate, composed of three joints, without terminal 



style. « 8 



8. Face bare, except on oral margin. 9 



Face pilose or liairy, more convex. ...... 10 



r-Tra- 



