Key to British genera of Colydiidae

1 Antennae stout, segments 4-9 transverse with rather dense, long outstanding setae around the apex of each, terminal segment roughly quadrate, slightly narrower than penultimate. Orthocerus Latreille
-- Antennae otherwise 2
2 Antennae distinctly clubbed or gradually broader towards apex. 3
-- Antennal segments 1-9 transverse, of equal width so that the antennae appear parallel, and with a weakly defined two segmented club. Pycnomerus Erichson
3 Pronotum transverse with wide explanate margin 4
-- Pronotum quadrate or elongate, if slightly transverse then without broad explanate margin 5
4 Elytra with raised areas, strongly crenulate at sides. Head strongly raised above antennal insertions and in front of eyes. Sides of pronotum unevenly and strongly dentate, front angles protruding and sharp, surface longitudinally sculptured. Antennae weakly clubbed, two separate segments of which are obvious. Endophloeus Dejean
-- Elytra simple; without raised areas, not crenulate at sides. Head without prominences. Pronotum very finely crenulate at sides, with impressions towards base, front angles protruding and rounded. Antennal club circular, separate segments not visible. Cicones Curtis
5 Pronotum with longitudinal ridges for entire length, anterior angles distinctly produced. 6
-- Pronotum without longitudinal ridges for entire length, anterior angles not, or only weakly, produced. 7
6 Pronotum with three longitudinal ridges which continue onto elytra. Langelandia Aube
-- Pronotum with four longitudinal ridges not continued onto elytra. Bitoma Herbst
7 Each elytral interstice with a row of scales. Pronotum rugose and so dull, without depressions, sides crenulate and front angles weakly produced. Antennal club subcircular, separate segments not obvious. Synchita Hellwig
-- Elytra without scales on interstices. Pronotum not rugose but dull due to microsculpture, front angles not produced. Antennal club (sometimes weakly) elongate with separate segments obvious. 8
8 Alternate elytral interstices raised and convex. Head slightly narrowed in front of eyes, front edge of clypeus about as broad as distance between eyes. Pronotum with a deep longitudinal impression at centre. Colydium Erichson
-- Elytral interstices flat. Head strongly contracted in front of eyes, front edge of clypeus much narrower than distance between eyes. Pronotum with four longitudinal impressions, widened towards base. Aulonium Erichson
See also family description.