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 R1 joins it; R1 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 R1. Drosophila, Phortica, and other genera. Drosophilidæ
ll. With another combination of characters.
m. The cell M and first M2 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 M2 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.
jj. Squamæ well developed, usually large, the lower one frequently projecting from below the upper one; both posthumeral and intraalar macrochætæ present; thorax with a complete transverse suture; postalar callus present and separated by a distinct suture from the dorsum of the thorax; front of the female broad, of the male frequently narrow, the eyes then nearly or quite contiguous; the connectiva adjoining the ventral sclerites either visible or not; hypopleural macrochætæ present or absent; subcosta always distinct in its whole course, R1 never short. Calyptrate Muscoidea[J]
k. Oral opening small, mouth parts usually much reduced or vestigial. This family is undoubtedly of polyphyletic origin but for convenience it is here considered as a single family. Oestridæ.
l. The costal vein ends at the tip of R4+5, M1+2 straight, not reaching the wing margin, hence cell R5 wide open ([fig. 163j]); squamæ small; arista bare; ovipositor of the female elongate. Larvæ in the alimentary canal of horses, etc. Gastrophilus