k. Subcosta present, distinctly separated from R_1 at the tip; R_1 usually ends distad of the middle of the wing; the small basal cells of the wing distinct. l. A bristle (vibrissa) on each side of the face near the margin of the mouth. CORDYLURIDÆ, SEPSIDÆ, PHYCODROMIDÆ, HETERONEURIDÆ, HELOMYZIDÆ. ll. No vibrissæ present. m. Head nearly spherical, cheeks broad and retreating; proboscis short; the cell R_5 closed or narrowed in the margin; legs very long; tarsi shorter than the tibiæ. CALOBATA and other genera. MICROPEZIDÆ mm. Flies with another combination of characters. RHOPALOMERIDÆ, TRYPETIDÆ, ORTALIDÆ, SCIOMYZIDÆ. kk. Subcosta absent or vestigial, or if present, then apparently ending in the costa at the point where R_1 joins it; R_1 usually ends in the costa at or before the middle of the wing. l. Arista long plumose, or pectinate above; oral vibrissæ present; anal cell complete; costa broken at the apex of R_1. DROSOPHILA, PHORTICA, and other genera. DROSOPHILIDÆ ll. With another combination of characters. m. The cell M and first M_2 not separated by a crossvein; anal cell absent; front bare or only bristly above; usually light colored flies. HIPPELATES, OSCINUS, and other genera. (See also m m m.) OSCINIDÆ mm. Cell M and cell first M_2 often separated by a crossvein; anal cell present, complete, though frequently small; scutellum without spines or protuberances; oral vibrissæ present; arista bare or short plumose; front bristly at vertex only; small dark flies. PIOPHILA (fig. 99), SEPSIS and other genera. SEPSIDÆ mmm. The GEOMYZIDÆ, AGROMYZIDÆ, PSILIDÆ, TRYPETIDÆ, RHOPALOMERIDÆ, BORBORIDÆ and DIOPSIDÆ differ in various particulars from either the OSCINIDÆ and the SEPSIDÆ noted above.