792 AN INTRODUCTION TO ENTOMOLOGY 



G. Subcosta vestigial or only basally indicated as a fold; costa 

 fractured but once; cell M and anal vein wanting; ocellar tri- 

 angle large and conspicuous; head bristles but feebly developed. 



p. 860 , Chloropid^ 



GG. Subcosta developed basally at least; ocellar triangle in most 

 cases not conspicuous; head bristles well-developed. 

 H. Costa twice fractured, basally and near the tip of Ri; arista 



never feathered below, p. 859 EPHYDRiDiE 



HH. Basal fracture of the costa indistinct; cell Rs very long, 



the bounding veins converging, p. 860 AsTEiiDiE 



FF. Cell 1st A present though in some cases quite small. 



G. Basal cells M and ist A large; wings with a fold extending 

 across from the costal fracture to the tip of cell M; frontal 



triangle conspicuous, p. 859 Psilid^ 



GG. Basal cells M and ist A small; wings without a fold. 



H. Arista plumose, in rare cases pectinate; wing with two costal 



fractures; vibrissas present, p. 860 Drosophilid^ 



HH. Arista bare or pubescent; if in a few cases plumose then 

 costa of wing with but one fracture which is situated dis- 

 tinctly before the tip of Ri. 



I. Tormae large and distinctly projecting; vein Sc distinctly 

 isolated at its extremity; ocellar triangle large nearly attain- 

 ing the base of the antennae; costal fracture close to the 

 tip of Ri. p. 859 Canaceid/E 



II. TormEB small and not projecting, or differing in other 

 characters. 



J. Anterior part of the "front" not bristly; postvertical 

 bristles not converging; cells M and 1st M2 not confluent; 

 Sc distinct to the tip; arista bare. p. 858. . . PiOPHiLiDiE 

 JJ. Not such flies. 



K. Costa broken twice; proboscis in most cases genicu- 

 late; postvertical bristles converging, rarely parallel or 

 wanting; anal vein in most cases vestigial or wanting. 



p. 862 MlLICHIID^ 



KK. Costa broken but once or proboscis not geniculate. 



L. Postvertical bristles divergent, in exceptional cases 



wanting; basal segment of the arista minute, shorter 



than broad; the so-called genae narrower than the 



buccce, except in Phytomyza in which cell ist M2 is 



open distally. p. 861 Agromyzid^ 



LL. Postvertical bristles converging, or if wanting Cell 

 R5 long and narrowed in the margin of the wing; 

 or cells M and ist M2 confluent, or proboscis genicu- 

 late, or arista plumose; basal segment of arista 

 longer than wide; the so-called genae as broad as or 

 broader than the buccas. p. 861 . . . .Geomyzid^ 

 AA. At least the lower lobe of the alulae or calypteres well-developed; the sub- 

 costal vein distinct in its whole course; vein Ri never very short; thorax 

 with a complete transverse suture; and the postalar callus present. (Sub- 

 section II. — Calyptratae). 



B. Proboscis usually much reduced or vestigial, not functional; mouth-open- 

 ing small. (Bot-flies). 



C. Costa ends at or slightly beyond the tip of vein R4 -f- 5; vein Mi + , 

 extends in a nearly straight line toward the outer margin of the wing 



p. 864 Gastrgphilid^e 



CC. Costa extends to the tip of vein Mi + 2; vein Mi -f 2 with a bend so 

 that cell Rj is much narrowed or closed at the margin of the wing. p. 866. 



OISTRIDiE 



BB. Mouth-opening normal; mouth-parts functional. 



