2i 4 NORTH AMERICAN DIPTERA. 



TABLE OF OENERA. 

 i. 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- 

 fnrca. ........... 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 (Coquilletlia, 



preoc.) Spogrostylum. 



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 {Argyramceba) 

 (5) Spog-ostylum. 



5. Pulvilli distinct (IO, 10a, 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 



(Stonvx) Anthrax. 



Two submarginal cells normally present. .... n 



