^ 



3G NORTH AMERICAN DIPTERA. 



2. Throe posterior cells Bittacomorpha AVestwood. 



Four posterior cells. ..... Ptychoptera Meigeii. 



TI PULING. 



1. Legs long and slender, especially the tarsi ; anterior branch of the 

 second vein absent, obsolete or periiendicular, the r]iondjoi<l cell 

 more or less square. ......... 2 



Legs not unusually slender, anterior branch of second vein jiresent and 

 oblique. ........... 5 



2. Antennae tliirteen-jointed ; male forceps complex. 



Doliciiopeza Curtis. 



Antennae with less than thirteen joints; male forceps small, sinii)le. o 



3. Fifth posterior cell not in contact with discal cell. 



Megistocera Wedemaiin. 



Fifth posterior cell in contact with discal cell. .... 4 



4. Head on a neck-like prolongation of the thorax; seventh vein short 

 running into the anal angle. . Brachypremna Osten Sacken. 



Head more closely applied to the thorax ; seventh vein terminates in the 

 margin at some distance from the anal angle. 



Tanypremna ()sten Sacken. 



5. Antenna; of ^ pectinate or sub-pectinate. ..... 



Antenna" not iiectinate. ........ 7 



r>. Ovipositor of 9 loig> sword-like. . . . Xiphura Brulle. 



Ovipositor of 9 long but not sword-like. . Ctenopiioua Meigen. 



l.^^XirTife posterior veins arising from the discal cell, the two anterior 

 sometimes arising together but the petiole always siiort. 



Pachyrhhina Macquart. 



5V0 posterior veins arise from the discal cell the anterior one furcate, 



^ petiole always of considerable length. ..... 8 



8. Antennae serrate ; northern s])ecies. . . Stygeropis Loew. 

 Antenna^ not serrati' beh)w. . 9 



0. Marginal vein wanting, but one margin.al cell, antennal Joints sliort with 

 minute bristles. ...... Hoi.oui^sia Loew. 



Two marginal cells. . 10 



10. Abdomen slender, very long; antenna' coni])osed of twelve joints. 



LoxGURik Loew. 

 Abdomen less elongate; antenna' with tliirteen joints. TiPULA\Linne. 



