The True Flies 



43 — Third joint of the antennae noticeably longer than broad 



Family Scatophagidce. 



Third joint broader than long, the last section of the fourth 

 vein usually much longer than the preceding section. . . 

 Family Heteroneuridce. 



44 — Front edge of the wings not beset with spines (Sepsidce, in 

 couplet 51). 



Front edge of the wings beset with short spines, thorax con- 

 vex, third joint of the antennae nearly circular 



Family Helomy^idce. 



45 — Tibiae bearing an erect bristle on the outer side before the 

 apex, anal and basal cells present 46 



Tibiae not furnished with such a bristle, anal cell present. .48 

 46 — Body convex, the face and cheeks not unusually bristly. . .47 



Body greatly depressed, the face and cheeks unusually bristly 

 Family Phycodromidce, 



47 — Sixth vein of the wings prolonged to the wing-margin. . . 

 Family Sciomy^idce 



Sixth vein obliterated before reaching the wing-margin .... 

 Family Sapromy^idce 



48 — Legs usually short and robust, abdomen usually ovate and 

 rather short, in the female furnished with a horny ovi- 

 positor 49 



Legs and body usually very elongate and slender, abdomen of 

 female not furnished with a horny ovipositor, bristles of 

 the front confined to the upper half 51 



49 — Basal and anal cells large, the latter usually prolonged at its 

 lower apical angle 50 



Basal and anal cells small, the latter not prolonged at its 

 lower apical angle, bristles of the front confined to its 

 upper half Family Lonchceidce. 



50 — Auxiliary vein gradually curving to the costa toward its apex, 



bristles of the front confined to the upper half 



Family Ortalidce. 



Auxiliary vein abruptly bent forward near its apex, bristles 

 of the front extending from the vertex almost to its 

 lower end Family Trypetidce. 



51 — Face in profile retreating on its lower part, palpi usually 

 large, third and fourth veins usually strongly converging 



toward their apices Family Micrope^idce. 



91 



