#2
This will classify most holarctic Cecidomyiidae, but there are exceptions. Note that R-M is a longitudinal vein in Cecidomyiidae (like in Sciaridae).
Lestremiinae: Five tarsomeres, first longer than second, usually more complete wing venation, ocelli often present, antennae often with fewer than 12 flagellomeres. If you can make out five normal tarsomeres (first longest) or ocelli, it must be Lestremiinae (s. lat.; the subfamily has recently been split).
Porricondylinae: First tarsomere very short (rarely absent) and nearly fused to second, vein Rs strong, vein R-M often bowed out towards hind margin of wing.
Cecidomyiidi: First tarsomere very short (never long or absent) and nearly fused to second. Vein Rs weak, interrupted or absent. R-M nearly straight. Typically with 12 flagellomeres separated by distinct necks. In females, the flagellomeres are cylindrical (except for necks) with a ring of hairs at each end giving them a slightly dumbbell shaped appearance. In males, apparently with 24 flagellomeres because each flagellomere is apparently divided.
Lasiopteridi: Legs and wings as Cecidomyiidi. Typically not with 12 or 24 flagellomeres, and typically not with dumbbell shaped flagellomeres separated by necks.
