214 



NORTH AMERICAN DIPTERA. 



TABLE OF GENERA. 



1. The bifurcation of the second and third veins takes place opposite 



or nearly opposite the anterior cross-vein, the distance not ex- 

 ceeding the length of the cross-vein; the second vein forms a 

 knee at its origin, the third vein in a straight line with the pre- 

 furca. ........... 2 



The bifurcation of the second and third veins takes place at a 

 greater distance from the cross-vein, usually at an acute angle. 12 



2. Antennal style distinct, that is it is separated from the third joint 



or the styliform prolongation of the joint by a distinct suture. 3 



The third joint not with a distinct, suturally separated style, the 



style when present very minute. ..... 7 



3. Antennal style with a pencil of hairs at the tip; pulvilli distinct; 



front tibiae with bristles. . . .... 4 



Antennal style not terminating in a pencil of hairs; three or four 

 submarginal cells present. ....... 5 



4. Outer submarginal cell bisected by a cross-vein (Coquillettia, 



preoc.) Spogostylum. 



Outer submarginal cell not bisected by a cross-vein; the anterior 

 branch of the third vein sometimes connected with the second 

 by a cross-vein forming three submarginal cells (Argyramosba) 

 (5) Spogostylum. 



5. Pulvilli distinct (1O, lOa, p. 80) Aldrichia. 



Pulvilli vestigial or wanting. ..*.... 6 



6. Outer submarginal cell divided by a cross-vein, making four sub- 



marginal cells (2) Hyperalonia. 



Outer submarginal cell not divided by a cross-vein; posterior claws 

 with a basal tooth (fig. 85, 3, 4, 8) . . . Exoprosopa. 



7. Eyes of male contiguous at the vertex; anal cell closed. 



Astrophanes. 

 Eyes of male not contiguous at vertex; anal cell open. . . 8 



8. Anal cell widest at the middle. ...... 9 



Anal cell widest at the margin. ..... Mancia. 



9. The second vein strongly contorted at the distal end in the shape 



of a recumbent letter S; three submarginal cells present. 



Dipalta. 

 The second vein not so contorted at end. . . . . 10 



10. Three submarginal cells normally present; proboscis elongate 



(Stony.r] Anthrax. 



Two submarginal cells normally present. . . . .11 



