Key to species of Massartella mature nymphs

1 Gills present on abdominal segments I–V................................................. Massartella alegrettae

- Gills present on abdominal segments I–VI.................................................................. 2

2 Dorsal portion of gills with well-developed apical process (Fig. 15); abdominal sterna with prominent thick setae................................................................................................ Massartella brieni

- Dorsal portion of gills with short apical process or without apical process (Figs. 16–18); abdominal sterna glabrous........ 3

3 Dorsal portion of gills without apical processes (Fig. 17)...................................... Massartella devani

- Dorsal portion of gills with short apical process (Figs. 16, 18)................................................. 4

4 Mandibles with thick median hair tuft on outer margin................................... Massartella venezuelensis

- Mandibles with outer margin completely covered by a dense row of long setae...................... Massartella hirsuta