Key to the species of Gymnocychramus

1. Colour primarily dark reddish-brown or black (Fig. 6); prothorax wider than combined elytra; sides of pronotum broadly rounded and sides of elytra straight and slightly converging almost to apex; macropunctures on elytra placed more sparsely within longitudinal rows, the distances between them usually greater than a puncture diameter; prosternum strongly tumid; mesal lobe at apex of mentum subacute; ventral surfaces with a number of large, elongate-oval pits lining postmesocoxal lines and anterior edges of metacoxal cavities and occurring on all abdominal ventrites; dorsal lobe of penis (Figs 62–63) about as long as ventral lobe, deeply incised, with small tooth at base of incision; total length 4.70–6.20 mm (mean 5.54).................................................................................................... G. politus Lea

- Colour primarily reddish-orange, with elytra black (Figs 12, 23); prothorax as wide as or slightly narrower than combined elytra; sides of prothorax and elytra evenly, continuously curved; macropunctures on elytra placed more densely within longitudinal rows, the distances between them often less than a puncture diameter; prosternum weakly convex; mesal lobe at apex of mentum broadly rounded; ventral abdominal pits, if present, very small; dorsal lobe of penis (Figs 60–61) much shorter than ventral lobe, apically acute, not incised and without tooth; total length 3.00–5.00 mm (mean 3.98)...... G. bicolor sp. nov.