Description

All members of the family are small, 0.8-5.2mm although most are between 1.5 and 3.0mm, and among the largest are species of Antherophagus Dejean, 1821 of which 3 are included in the UK fauna. The form varies; most are either elongate, rather parallel-sided and to some degree flattened, or oval and convex, the colour varies from black or rich red-brown to pale testaceous and many are bicoloured or have contrasting maculae etc. Most are distinctly pubescent, usually this is fine and recumbent but sometimes erect or semi-erect and in 2 or 3 distinct layers, and most are devoid of discreet sensory setae. The head is elongate and often retracted into the prothorax to the posterior margin of the eyes, usually smooth and variously punctured, sometimes with a longitudinal impression on the vertex and with (Atomaria Stephens, 1829 and Ephistemus Stephens, 1829) or without (most genera) a distinct frontoclypeal suture. The clypeus is quadrate or nearly so, mandibles curved and sharp, with a distinct internal mola and in some with a dorsal tubercle but without impressed mycangia, labrum transverse; sometimes with a transverse ridge or line and sometimes produced into a median process. Labial palps 2-segmented; equal in width in e.g. Cryptophagini, or with the basal segment distinctly wider in e.g. Atomarinae or Caenoscelini. Antennae almost always 11-segmented with a loose 3-segmented club, the basal segment is wide and conical or rounded laterally, and often curved, intermediate segments often quadrate or slightly elongate and sometimes, as in many Atomaria, with alternating long and short segments. Insertions anterior or lateral in front of the eyes and visible from above, in Ephistemus with antennal grooves under the head and pronotum. Eyes usually convex and prominent, with fine facets and with or without setae, temples short and narrowed to the base but sometimes developed; in the monogeneric Thortus Bran, 1893 from New Zealand they are produced laterally behind the eyes. Pronotum quadrate to transverse, weakly convex, smooth and variously punctured and pubescent, in some Cryptophaginae with distinct fovea towards the base and in some Atomariinae with a transverse depression parallel to the basal margin, lateral margin variable; curved and broadest at the base or about the middle to parallel-sided, with a well-developed marginal bead although absent in Hypocoprini and present only towards the base in some Atomariinae. Base generally as wide as the elytral base, posterior angles not produced, lateral margins variously smooth or toothed; in Cryptophaginae often distinctively toothed near the middle or produced or toothed behind the anterior angles. Prosternum quadrate to elongate in front of rounded and separate, externally open or closed coxal cavities, prosternal process well-developed, arched or flat, broadly rounded to obtuse or truncate apically and often overlying the base of the mesosternite. Mesosternum short with separate coxal cavities closed laterally by the metasternum. Metasternum elongate, without a transverse groove but sometimes with a long median impression, coxal cavities transverse and widely to narrowly separate. Abdomen with 5 free ventrites, basal ventrite longer and usually produced between the metacoxal cavities. Elytra completely covering the abdomen or very nearly so, epipleura well-developed in the basal half only, often absent behind the middle, surface smooth; apunctate to finely or strongly punctured, without striae, at most with ill-defined puncture rows. Legs slender and relatively long. Pro- and mesocoxae recessed into cavities, posterior coxae not recessed to receive the femora. Trocanters relatively long, about one-quarter the tibial length. Femora parallel-sided and straight to weakly curved, sometimes weakly expanded about the middle or towards the apex. Tibiae parallel to weakly expanded towards the apex, without prominent teeth or spurs and generally with 2 small spurs on the inner apical angle. Tarsi 5-5-5, 5-5-4 or 4-4-4, sometimes sexually dimorphic; 5-5-5 in the female and 5-5-4 in the male.

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Cryptophagids generally may be recognized by the following combination of characters: small size and in many cases (with a little experience) characteristic appearance, head exposed with the antennal insertions visible from above, antennae with a distinct or gradual 3-segmented club (rarely 1 or 2 segmented), mandibles lacking mycangium, pronotum bordered (except in Hypocoprini), elytra randomly punctured and with well-developed epipleura (at least in the basal half), basal abdominal ventrite longer than the others and mesocoxal cavities closed by the metasternum. Many species of Atomariinae are sexually dimorphic in body shape and antennal morphology. Specific identification can be very difficult and dissection is often necessary. There are no up to date keys to the family in English, Joy’s Handbook will reliably key out to genera and there is a guide to species of Cryptophagus (Coombs, C.W. & Woodroffe, G. E., 1955. A revision of the British species of Cryptophagus (Herbst) Transactions of the Royal Entomological Society of London. 106: 237-282), and beyond this there is an on-line key Here.