ee. Claws tridentate ([fig. 161 f.]).
f. Anal cell closed at apical margin by the anal crossvein.
g. Ocelli absent. Stilbometopa Coq.
h. R4+5 does not form an angle at the crossvein. On birds. There is a record of one species of this genus attacking man. Ornithomyia Latr.
hh. R4+5 makes an angle at the crossvein. O. confluens. Ornithoica Rdi.
ff. Anal cell not closed by an anal crossvein. Lynchia, Pseudolfersia, and Olfersia are chiefly bird parasites. The first mentioned genus is said to be the intermediate host of Hæmoproteus columbæ.
aa. Abdominal segments chitinous; not parasitic in the adult stage.
b. Antennæ with six or more segments and empodium not developed pulvilliform; palpi often with four segments.
c. Ocelli present. Blepharoceridæ, Rhyphidæ, Bibionidæ, Mycetophilidæ, besides some isolated genera of other families.