Key to species of Malacophagomyia (males only)

1 Parafacial and fronto-orbital plate with silvery microtomentum (Figs 1–2). Abdomen brown or reddish with gray microtomentum, T5 with lateral spots of silvery-gray microtomentum (Figs 7, 8). Surstylus small, elongated or rounded. Cerci with short

setae or with long villous setae on basal 1/ 2 in dorsal view..................................................... 2 - Parafacial and fronto-orbital plate with golden microtomentum (Fig. 3). Abdomen black with gray microtomentum, T5 with latero-ventral part reddish, with lateral spots of light golden microtomentum (Fig. 22). Surstylus conspicuously large, broad, with rounded tip (Fig. 28). Cerci with long villous setae on basal 3/ 4 in dorsal view (Fig. 27).......... M. rivadavia sp. nov. 2 Syntergosternite 7+8 blackish. Cerci short (cerci length 2X cerci width), covered with short setae (Fig. 12). Arms of ST5 with several fine setae on its inner surface, and short posterior lobes (Fig. 4).................................. M. filamenta

- Syntergosternite 7+8 reddish. Cerci elongated (cerci length 3X cerci width), covered with long villous setae on basal half (Fig. 19). Arms of ST5 with strong spine-like setae on inner surface, and elongated posterior lobes (Fig. 5)......... M. kesselringi