Description

All members of the family are small, 1.3-6.0mm and rather drab insects; most vary from some shade of brown to black and a few have lighter or darker markings and in this respect such species tend to be variable. Some species are metallic and the dorsal punctation varies from fine to very coarse and while some are glabrous most are to some extent pubescent. Habitus broadly elongate and rather depressed, with the elytra truncate leaving the pygidium as well as one or two, e.g. in Brachypterus, exposed abdominal tergites. The penultimate tergite is often produced backward laterally and this is a good guide to the family. Head prognathous and generally only weakly constricted behind the eyes, an occipital ridge is distinct in the Nearctic Anthonaeus agavensis but otherwise absent. The eyes are moderately convex and usually strongly protruding; glabrous and in most species with fine facets. Antennal grooves or ridges absent, the vertex and frons smoothly convex to almost flat and a frontoclypeal suture absent or only faint. The surface is variously punctured and pubescent. Mandibles short and sharp, and rarely visible from above, maxillae with galea and lacnia. Antennae inserted under the anteriolateral margin between the eyes and the mandibles; 11-segmented with a usually loose and weakly defined 3-segmented club, even when this is strongly defined the club is proportionally much narrower than in the superficially similar Nitidulidae. A single genus, Sibirhelus Kirejtshuk, 1989, with one Siberian (Irkutsk) species, lacks a club; here the antennae are gradually thickened towards the apex. Basal segments sometimes sexually dimorphic, being enlarged in the males, and sometimes greatly so e.g. in some Kateretes, but never with a curved scape. Pronotum quadrate to transverse and generally broadest behind the middle, the form of the hind angles varies from rounded to angled or produced posteriorly as in Brachypterolus. The lateral margins are finely bordered and either evenly rounded, sinuate or constricted in front of the hind angles. The posterior margin varies from almost straight to strongly sinuate and produced backwards medially. The post-coxal cavities are only partially closed posteriorly. Scutellum usually large and obvious, varying from transverse and triangular to curved. The elytra are broadly elongate and at least to some extent rounded laterally, the hind margin truncate, oblique or weakly curved and the surface lacks striae, the punctation random and varying from fine to very strong. The elytral pubescence varies and some species appear glabrous. Lateral margins finely bordered and this is visible from above only towards the base, not explanate or raised (as in some Nitidulids). The dorsal microsculpture is very variable. The hind wings are generally well developed. Legs robust; apical part of all femora visible from above, tibiae widened towards the apex with lateral margins lacking carinae or spines, each with 2 apical spurs on the inner angle, Tarsi 5,5,5; pseudotetramerous, segments 1-3 bilobed, sometimes strongly so and often with densely pubescent pads underneath. Claws toothed or simply thickened towards the base. Abdomen with 5 ventrites, the first sometimes with postcoxal lines. In males the eighth tergite is sometimes exposed and the fourth sometimes has a tomentose area. Pygidium large, deflexed and always obvious from above. The U.K. species are easily recognized by the exposed abdominal tergites, one of which is usually produced backwards laterally, and the gradually clubbed antennae.