17 (16). Wings flat over D; X on middle of wing.
18 (19). Veins hairy (plate IV, 13).
Culicidæ, IX
19 (18). Veins bare.
19a (19b). Antennæ long; V, 4 and V, 2 forked; X, 4 (plate IV, 14) ending in V, 2.
Dixidæ, X
19b (19a). Antennæ very short but 11-jointed; no veins forked.
Orphnephilidæ, VII
20 (5). Thorax (plate VI, 32) with a strong cross seam.