2 86 NORTH AMERICAN DII'TERA. 



7. Body elongate; abdomen narrower than the thorax. . . 8 

 Body short; abdomen as broad as the thorax. ... 9 



8. The hyaline triangle at tip of first vein does not cross the third 



vein (IO) Straussia. 



The hyaline triangle at tip of first vein crosses the third vein. 



Molynoccelia. 



9. The horizontal diameter of the eyes remarkably short. Stenopa. 

 Horizontal diameter of eyes not shorter than usual. . . 10 



10. Antepenultimate sectioir of fourth vein straight. . Acidia. 

 Antepenultimate section of fourth vein curved. Epochroa. 



11. Coloring of the body general light, never black. . . 12 

 Coloring of the body black. ....... 16 



12. Wings near the middle with two cross-bands, converging toward 



the posterior margin. ....... 13 



Wings not with such cross-bands. ..... 14 



13. The third longitudinal vein is gently curved backward toward the 



tip; head not swollen Spilographa 



Third longitudinal vein straight to the extremity; head distinctly 

 swollen (12). Oedicarena. 



14. Wings with four very oblique cross-bands. .... 15 

 Cross-bands nearly transverse, or dissolved into spots; cross-veins 



but little oblique Trypeta. 



15. Scutellum tumid, bituberculate Peronyma. 



Scutellum of the usual structure, not swollen, though convex (16). 



Plagiotoma. 



16. Cross-veins conspicuously approximated. ...517 

 Cross-veins not approximated 18 



17. Wings with hyaline indentation and a subapical, arcuate hyaline 



cross-vein; scutellum black (15). . Polymorphomyia. 

 Wings with three brown bands or projections, connected anterior- 

 ly, the distal one following the costa, the middle one beyond 

 the middle of the wing, the proximal one toward the base (7) . 



Oedaspis. 



18. Scutellum with four bristles, yellow; wings with black cross-bands. 



Rhagoletis. 

 Scutellum with two bristles, black; wings with hyaline indenta- 

 tions along the margin (26). .... Aciura. 



