2 NOKTII AMERICAN DIPTJ^RA. 



o. Dorsum of thorax with a compk'tf V-sliaped suture;* wings (wanting 

 rarely) many-veined, often witli a complete discal cell; ocelli want- 

 ing (present in a few forms); often large flies. . . Tipuhd.k. Xy 

 Dorsum of thorax without a V-sliaped suture, or rarely with any 

 transverse suture. .....:... 4 



4. A comjilete discal cell present; empodia developed pulvilliform, the 



pulvilli rudimentar\\ ...... Kiiyphio.i:. ^C? 



No discal cell. 5 



5. Antenna? composed apparently of three joints with a terminal arista ; 



small species, three or four millimeters in length. ORPHNEPiiiLiDiE. ^2^ ^ 

 Antenna2 not apparentlj^ composed of tlirce joints and a terminal 

 arista. ........... 



0. Wings with only a few longitudinal veins, and no cross- veins; coxae not 

 elongate, tibia? without' terminal spurs, legs not thickened; ocelli 

 present or absent; small or minute, delicate, mostly gall-producing 



flies. Cecidomyid.t:. J 



Not such flics ; wings usually many-veined. .... 7 



7. Ocelli present 8 



Ocelli wanting (compare MijcetophlUdu). ..... 10 



8. Wings broad, bare, characteristically marked by numerous folds be- 



tween the veins, giving a netted, spiderweb-like apj)earance. 



Wings not so marked ; no entire transverse suture. ... 



9. Coxae much elongated (moderately so in Sciarinrp); antennae often elon- 



gate, the joints constricted ; three or two ocelli present (in the latter 

 case one situated neareach eye and often perceptible with difficulty); 



all the tibiae with spurs Mycetopiiilid.k. /3 



Coxa? short, the thorax rounded, not humped above; antenna? shorter 

 than the thorax, thickened, the joints closely united without marked 

 constrictions ; legs strong, the front femora often thickened ; empodia 

 pulvilliform, the pulvilli sometimes absent ; eyes of 5 large. 



BiBIONIDiE. 3 



10. The costal or marginal vein does not extend beyond the tip of the 



wing. 11 



The marginal vein encompasses the entire wing. ... 12 



11. Antennae slender, the joints more or less constricted, and often bushy 



plumose; legs slender, hind tibia? and metatarsi never dilated ; abdo- 

 men slender; wings narrow. .... Chironomid.e. X-'^ 



* Bittctcomorpha, Ptijchoptera and Jdiojdasta ma\- cause doubt here. They 

 have the suture incompletely V-shaped and sinuous. Compare RJii/phida . 



