Couplet 131

131a:  Antenna with 10 antennomeres, club of only 1 antennomere; elytra > 2X as long as wide (Rhizophaginae)

Monotomidae   p. 430

131b:  Antenna with 10 or 11 antennomeres, club of 3 or more antennomeres; elytra < 2X as long as wide