30 



when situated near the middle of tlie length of the segment, and mar- 

 ginal when located near its posterior margin. 



The veins and cells of the wings are called by the same terms as in 

 the other families of Diptera, except that the first posterior cell is com- 

 monly called the apical, and the portion of the fourth vein beyond the 

 bend is sometimes termed the apical croHsvcin. 



TABLE OF GENERA. 



The only attempt at publishing a synoptic table, comprising all of the 

 genera rei)orted as occurring in North America, is that by Mr. Vj. H. T. 

 Towiisend, in the Proceedings of the Entomological Society of Wash- 

 ington ' and in the Transactions of the American Entomological Soci- 

 ety.^ That in the former publication is a reprint of the table given by 

 Dr. Schiuer,^ and that in the latter a reprint of the one by P. M. van 

 der Wuli^,^ both modified so as to comprise only the "North American 

 genera. As the author did not liave access to specimens of many of 

 these genera, and as the (characters he uses are in many cases not of 

 specific, much less of generic, value, the result is not altogether satis- 

 factory, and I have therefore constructed an entirely new table, 

 ■which, however, includes only those genera from America north of 

 IMexico of which 1 have examined representatives. A list of the remain- 

 ing genera reported from this region is given at the end of the table. 



In some cases doubt will arise as to which section a given genus 

 should be referred, but in such cases, at least so far as they occur to 

 the writer, the genus is placed in both sections: 



1. Abdomen provided with true macrochivtip 8. 



Abdomen destituti' of macrochiEtiu, apical cell ending at or near the extreme 



wing tip - 2. 



2. Upper side of abdomen very convex, abdomen siibhcmispherical, sides of face 



bare - 3. 



Upper side of abdomen flat, or the abdomen elongated and cylindrical 4. 



3. Antenn;T3 not reaching lower third of face (p. 42) Cistoffanter. 



Antennse reaching lowest fifth of face, or even lower (p. 43) Gyvmosoma. 



4. Hind tibiic outwardly not ciliate with scales 5. 



Hind tibiio ciliatowith nearly erect scales, sides of face bare., (p. 47) Trichopoda. 



5. Sides of face bare (!. 



Sides of face bristly, third and fourth veins almost e([ually converging toward 



their tips, which meet or almost meet each other (p. 49) GymnophnnUi. 



6. I'roboscis at most slightly longer than the head, geniculate near the base oulv, 



antenna; at most reaching slightly below middle of face, apical cell closed, the 



petiole at least twice as long as the small crossveiu 7 



Proboscis bristle like, almost as long as the body, geniculate near the base and 

 also near the middle (p. 49) is mm ip i M»( t . 



1 Vol. II. pp. 92 to 99 ; April 2, 1891. vJ 



*Vol. XIX, pp. 134 to 141 ; June, 1892. 



^Fanna Austriaca, Diptera, Vol. I, pp. LXX to LXXI; 18(52. 



•• Biologia Centrali-Americana, Diptera, Vol. II, pp. 5 to 7, and 41 to 44 ; 1888 and 1890. 



