ii. Face linear; small basal cell of the wing absent. One species, P. furcatum, from California. Parasimulium Malloch
gg. Flies of a different structure.
h. Antennæ composed of apparently two segments and a terminal arista formed of a number of closely united segments. Rare flies with aquatic larvæ. Orphnephilidæ
hh. Antennæ of six to fifteen segments, those of the male usually plumose; legs frequently slender and wings narrow Chironomidæ
i. Media forked (except in the European genus Brachypogon); thorax without longitudinal fissure and not produced over the head (except in four exotic genera); antennæ usually fourteen-jointed in both sexes; fore tibia with a simple comb of setulæ, hind tibia with two unequal combs, middle tibia without comb. Ceratopogoninæ
j. Thorax produced cap-like over the head, wing narrow and very long. Jenkinsia, Macroptilum and Calyptopogon, eastern hemisphere; Paryphoconus, Brazil.
jj. Thorax not produced over the head.
k. Eyes pubescent, empodium well developed, or if short then R2+3 distinct and crossvein-like or the branches of R coalescent; r-m crossvein present; fore femora not thickened; wing either with appressed hairs or with microscopic erect setulæ. Dasyhelea Kieff.
kk. Eyes bare, or otherwise differing from the foregoing.
l. Empodium well developed, nearly as long as the claws and with long hairs at the base; femora and fifth tarsal segments unarmed, i.e. without spines or stout setæ; fourth tarsal segment cylindrical.