106 NORTH AMERICAN DIPTERA. 



short; no auxiliary vein ; third and fourth longitudinal veins 

 parallel or divergent ; posterior basal united with the discal 

 cell ; anal cell wholly wanting or rudimentary. Legs short ; 

 femora sometimes thickened ; tibiae without preapical bristle. 

 This group of flies is always sure to be represented by nu- 

 merous specimens and species in any collection of diptera. 

 The flies are very common and are collected in large numbers 

 by the sweep-net, from rank growing grass and meadowlands. 

 The larvae of several species of Oscinis have been bred from 

 wheat, barley, oats, rye and grass stems and Phragmites ; 

 those of Oscinis have similar habits ; larvae of Siphonella from 

 Cirsium, etc. The larvae are thick, cylindrical, with stout 

 inoutli-hooklets ; abdomen with fleshy protuberances for loco- 

 motion ; the antennae two-jointed. 



TABLE OF GENERA. 



1. Head produced conically in front, the antennae elongate. 



ECTECEPIIALA Macquart. 

 Head not produced conically ; antennae not elongate. ... 2 



2. The costal vein reaches to the tip of the third longitudinal vein. . 3 

 The costal vein reaches to the tip of the fourth longitudinal vein. 5 



3. No posterior cross-vein ; first three longitudinal veins recurved. 



ELLIPONEURA Loew. 

 Posterior cross- vein present. . . 4 



4. Hind femora much thickened MEEOMYZA Meigen. 



Hind femora not thickened ; mesonotum usually with stripes. 



CHLOROPS Meigen. 



5. Ovipositor horny, subulate. . . . ; . OPETIOPHORA Loew. 

 Ovipositor not horny and subulate. . . 6 



6. Antennae with a thickened, porrect, style-like arista. 



ELACHIPTERA Macquart. 

 Antenna? with the usual bare, pubescent or rarely plumose arista. 7 



7. Oral margin of the face produced ; proboscis often elongate and folded 



back. . . . . - . . . SIPHONELLA Macquart. 

 Oral margin not produced. . 8 



8. Third joint of the antennae reniform, with a subterminal, short-plumose 



arista. ........ GAURAX Loew. 



Third antennal joint rounded or oval. . . ' . . . . 9 



