The True Flies 



Face perpendicular and somewhat projecting forward on its 

 lower part, palpi minute, third and fourth veins parallel 

 or diverging toward their apices Family Sepsidce. 



52 Femora and usually the body short and robust 54 



Femora slender and elongated, body also usually elongated, 

 anal cell present ^ 



53 Fourth vein parallel with or diverging from the third vein. . 

 Family Psilidce. 



Fourth vein usually curving toward the third at its apex 

 (Micrope^idce, in couplet 51). 



54 Head nearly hemispherical, not prolonged laterally 55 



Head prolonged laterally, the eyes situated at the apices of 



the prolongations, front femora very robust 



Family Diopsidce. 



55 Anterior oral margin bearing a distinct bristle on either 

 side 58 



Anterior oral margin not bearing such bristles 56 



56 Anal cell usually wanting, the second basal cell usually con- 

 fluent with the discal cell 57 



Anal cell distinct, second basal cell usually separated from the 

 discal cell ( Agromy%id& t in couplet 60). 



57 Antennal arista frequently long-pectinate on the upper side, 

 head usually much wider than high, face usually pro- 

 vided with bristles especially on each side, and the oral 



opening sometimes excessively large 



Family Ephydridce. 



Antennal arista never long-pectinate, head not wider than 

 high, face not bristly, and the oral opening never un- 

 usually large Family Oscinida. 



58 Arista of antennae bare, body short and robust 60 



Arista usually plumose; if bare the [body is some what 

 slender 59 



59 Hairs of the antennal arista long and few in number, second 



basal cell usually confluent with the discal cell 



Family Drosophilidce. 



Hairs of the arista short and numerous, sometimes wanting; 



second basal cell separated from the discal cell 



Family Geomy^idoe. 



92 



