1. Elytral pubescence single, entirely decumbent with hairs of approximately equal length............................................................................................... 2

– Elytral pubescence double, with longer sub-erect or obliquely raised hairs, sometimes arranged in rows, in addition to decumbent pubescence; or all hairs obliquely raised and uneven in length................................................ 6

2(1). Pronotal callosities strongly produced laterally so that pronotum is much wider across callosities than across lateral teeth; lateral tooth often very large (ratio of tooth projection from lateral margin/length of callosity: ̴ 40%). L. 1.9–2.8 mm....................................................... Cryptophagus acutangulus

– Pronotal callosities much less strongly produced, pronotum not or slightly wider across callosities than across lateral teeth; lateral tooth small to medium-sized (ratio of tooth projection from lateral margin/length of callosity: 13–24%)................................................................................................... 3

3(2). Face of apical pronotal callosity projecting out from lateral margin of pronotum, delimited posteriorly by a distinct angle............................................. 4

– Face of apical pronotal callosity not projecting out from lateral margin of pronotum, posteriorly contiguous with lateral pronotal margin................. 5

4(3). Pronotum noticeably narrower than elytra (ratio of elytra at humeri to pronotum at middle ̴ 1.0:1.2), almost parallel-sided, appearing quadrate (width to height ratio ̴ 1.0:1.2). L. 2.2–3.3 mm.................... Cryptophagus fallax

– Pronotum not or only slightly narrower than elytra (ratio ̴ 1.0:1.0), with arcuate lateral margins, distinctly transverse (ratio ̴ 1.0:1.5). L. 2.0–2.7 mm......................................................................................... Cryptophagus jakowlewi

5(3). Usually bi-coloured, pronotum and elytral humeri reddish, remainder of elytra darker; pronotal callosities large (̴ 1/4 of lateral margin), upturned, and not projecting anteriorly; lateral margin of pronotum strongly concave between callosity and lateral tooth. L. 2.0–2.8 mm................. Cryptophagus scanicus

– Unicoloured red-brown; pronotal callosities smaller (̴ 1/5 of lateral margin), not upturned and projecting strongly anteriorly; lateral margin of pronotum slightly concave between callosity and lateral tooth. L. 2.0–2.8 mm...................................................................................... Cryptophagus tuberculosus

6(1). Posterior edge of rim of pronotal callosity with a small posteriorly projecting rim tooth; flightless, most specimens with vestigial wings. L. 2.1–2.8 mm....................................................................................... Cryptophagus difficilis

– Posterior edge of rim of pronotal callosity without rim tooth; with full-sized wings......................................................................................................... 7

7(6). Pronotal callosity very large (̴ 1/3 of lateral margin); length ≤ 1.7 mm; antennal club with basal segment (article 9) distinctly narrower than middle segment (article 10). L. 1.5–1.7 mm..................... Cryptophagus mainensis

– Pronotal callosity smaller (̴ 1/4 or less of lateral margin); length ≥ 1.7 mm; antennal club with articles 9 and 10 of approximately the same width....... 8

8(7). Eyes small, conical, and somewhat flattened anteriorly; anterior elytral punctation significantly finer and more widely spaced than pronotal punctuation; generally smaller, most individuals ≤ 2.0 mm. L. 1.7–2.4 mm.................................................................................................... Cryptophagus laticollis

– Eyes normal to large; anterior elytral punctation almost as large and dense as pronotal punctuation; generally larger, individuals ≥ 2.0 mm..................... 9

9(8). Pronotal callosity generally smaller (1/5–1/6 of lateral margin) with weak dorsal rim, usually not prominent anteriorly. L. 2.5–3.0 mm...................................................................................................... Cryptophagus histricus

– Pronotal callosity generally larger (1/4–1/6 of lateral margin), usually thickened with strong dorsal rim, frequently prominent anteriorly. L. 2.0–3.0 mm......................................................................... Cryptophagus setulosus