MUSCIDEA. 99 



Tegulae small; eyes of male not more approximated than those of the 

 female, or, if so the narrowing is due to the less width of the median 

 stripe, the borders remaining the same (Muscida; acalyptratae, Ho/ome- 

 topa Brauer). . . . . . . .... . 7 



7. Auxiliary vein present, distinctly separated from the first longitudinal 



vein, terminating separately in the costa ; the first longituninal vein 



usually terminates at or beyond the middle of the wing. . 8 



Auxiliary vein absent, rudimentary or incomplete ; the first longitudinal 



vein usually terminates before the middle of the wing. . . 22 



8. A distinct bristle on either side of the face near the oral margin, i. e. 



oral vibrissae present. . . - . . . . , . 9 



No oral vibrissae. . . ..'... . . . 13 



9. Front on the sides and the vertex with long bristles. . ^ ; 10 

 Bristles confined to the vertex or the front bare. ... 12 



10. The distance between the anterior and posterior cross-veins (on the 



fourth longitudinal vein) very much less than from the latter to the 

 margin of the wing* i. e. the cross- veins approximated. 



HETKRONEURIDwE. 



Cross- veins not approximated. ..,,-. . . . . . 11 



11. Thorax flattened; head small; cheeks broad and bristly, the oral 



vibrissse in consequence not markedly differentiated ; bristly flies. 



PHYCODROMIDJE. 



Thorax convex ; head as broad or nearly as broad as the thorax ; cheeks 

 not markedly bristly. . . . . .. . SCATOMYZID^E. 



12. Abdomen elongate, narrowed at the base, usually cylindrical and de- 



curved posteriorly ; male genitalia usually prominent. SEPSIDJE. 

 Abdomen comparatively short and broad ; male genitalia but little or 

 not at all prominent; costa of the wings usually bristly. 



HELOMYZID^E. 



13. Antennae elongate and porrect; second joint as long or longer than the 



third, the latter usually with an angulated upper corner. . 14 



Antennas not elongated, or, if so, not porrect, the second joint always 



shorter than the third, the latter usually rounded at the end. 15 



14. Head in profile triangular, the face remarkably retreating ; hind tibise 



with or without a preapical bristle. " . . . . ORTALID.E. 

 Head not triangular in profile, the face perpendicular or but little re- 

 treating; front with two lateral orbital bristles; hind tibia? with a 

 preapical bristle (Tetanocerirue). . . . . SCIOMYZID^E. 



* The Agromyzince have the cross-vein approximated, but the auxiliary 

 vein is wanting. 



