Key to species of Elachistelmis gen. n.

1. Tarsal formula 4–4–4 (Figs. 15 & 17); hind wings with short setal fringe on posterior margin; apex of prosternal process pointed (Fig. 19); elytra quadrimaculate; median lobe of aedeagus 1.5 times as long as wide........... E. tetramera sp. n.

- Tarsal formula 5–5–5 (Fig. 25); hind wings with very short setal fringe, if present at all, on posterior margin; apex of prosternal process rounded (Fig. 23); elytra unicolorous or, at most, bimaculate; median lobe of aedeagus 1.2–1.3 times as long as wide.................................................................................. E. sipaliwiniensis sp. n.