58 Families and Genera of 



2. Anterior border of the mouth with vibrissa?. ... 3 

 Oral vibrisste not present. .... . .• . 7 



3. The distance between the anterior and posterior cross-veins (on 



tlie fourth vein) four or five times less than that between the 

 posterior cross- vein and tlie posterior margin of tlie wing. 



Heteroneurid.e 



The distance between these veins but little less or greater than 



that to the hind margin 4 



4. Abdomen elongate, usually cylindrical, narrowed at the base, 



behintl somewhat dccurved ; male genitalia usually clubbed, 



-projecting from the abdomen. 5 



Abdomen comparatively short and rather broad, never cylindri- 

 cal, or narrowed at the base ; male genitalia but little or not 

 projecting; wings large 6 



5. Front on the sides, and the vertex, with long bristles. 



^/etferOHCuVi CORDYLURIU.E 



Vertex, only, with long bristles ; body always shining black. 



Sepsid^ 



6. Proboscis horny, shining; hibella usually jiointed ; third anten- 



nal joint elongate ; males often woolly i^ilose. CoiiDYLURiD-E 

 Proboscis not horny or shining; third antennal joint short or 

 round ; males never woolly pilose. ?<> '•'■ ' »- , 



Phycodromidje, Helomyzid^ 



7. Antennae much elongate, and porrect; second joint as long or 



longer than the third Sciomvzid.i: 



Antenna not elongate, or, if so, decumbent ; second joint always 

 shorter than the third. ....... 8 



8. Two posterior basal cells very small and indistinct. 



LONCH.EID.E, SaPROMYZID.E 



Posterior basal cells large and very distinct. ... 9 



9. Hind tibije with a preapical bristle. . . . Sciomyzid.e 

 Hind tibiae without preapical bristle 10 



10. Front with bristles on the sides ; the auxiliary vein terminates 



steeply in the costa. ..... Trypetid.e 



F¥ont-bri*tly only on the vei'tex or upper part; the auxiliary 

 vein terminates acutely in the costa 11 



11. Legs elongate, often very long; abdomen slender and long, 



nearly cylindrical, often narrowed, or pedicellate at base. 12 

 Legs not elongate; abdomen never narrowed at base. Ortalid^ 



