12 species in Britain, 1-6mm long, oval to elongate, mostly brown, black or grey although Bitoma crenata (Fabricius) has orange elytra with a black saddle marking.  Most species are convex or flattened as a consequence of living beneath bark, though they can also be found in fungi, decaying vegetable matter (including potatoes decaying underground) or within the galleries of other wood-boring beetles.  One species, Endophloeus markovichianus (Piller and Mitterpacker) was last found in Britain in 1927 and is likely to be extinct here: Pycnomerus terebrans (Olivier) is only known in Britain from bronze age fossils and is no longer on the British list.