Key to American subfamilies, tribes, and genera of Nemestrinidae

1 Proboscis length reaching or exceeding posterior end of thorax................................................. 2

- Proboscis vestigial, or reduced, or reaching fore coxae........................................................ 4

2 Eyes bare; genital fork formed by solid plate divided into four branches (Falleniinae) (Fig. 28)........ Neorhynchocephalus

- Eyes densely pilose; genital fork formed by two or single H-shaped plate (Nemestrininae) (Figs. 31–33)................ 3

3 Genital fork formed by single H-shaped plate, complete (Fig. 31) or incomplete (Fig. 32); hypandrium reaching distal end of gonocoxites.............................................................................. Trichophthalma

- Genital fork formed by two superposed plates, with inner plate H-shaped (Fig. 33); hypandrium reaching base of gonocoxites................................................................................... T. (Eurygastromyia)

4 Posterior to R1, five veins reach apical margin of wing (Fig. 5); ocelli present, hypandrium reduced (Hirmoneurinae)...... 5

- Posterior to R1, three (or four) veins reach apical margin of wing; ocelli absent, hypandrium developed (Atriadopinae)................................................................................................. Atriadops

5 Eyes bare to densely pilose; frons projected forward and covered by dense pilosity (Hirmoneurini)..................... 6

- Eyes densely pilose; frons flat and covered by pollinosity or with a few sparse hairs (Hyrmophlaebini)................. 7

6 Face narrow, parallel-sided; antennae with three short segments; proboscis reduced, not exceeding length of head; genital fork formed by single, large H-shaped plate........................................ Hirmoneura (incl. Neohirmoneura)

- Face wide, trapezoidal-sided (Fig. 6); antennae with first segment 2x longer than second and third segments combined (Figs. 6–8); length of proboscis reaching fore coxae; genital fork cylindrical, U-inverted shaped (Figs. 24, 35), with bridge and arms of approximately same thickness, with corrugated ends (Figs. 25, 34, 36).......................... Bernardia gen. nov.

7 Genital fork formed by inverted U-shaped plate, incomplete (absent bridge) (Fig. 29)................... Hirmoneuropsis

- Genital fork formed by single inverted U-shaped plate, complete (bridge and arms), (Fig. 30).............. Hyrmophlaeba