There are five British representatives of family Cerylonidae: two Murmidius species found in stored products and three Cerylon species which occur in decaying ancient hardwood trees, particularly oak and beech.  They are thought to feed on the hyphae of fungi and slime moulds, and all are dark, elongate-oval, and small (1-3mm long).

A small family, Botheridae has just five British representatives, all small (1-3mm), dark, elongate often-shining species.  Four of these (Anommatus diecki Ritter, A. duodecimstriatus (Müller), Oxylaemus cylindricus (Panzer) and O. variolosus (Dufour)) are subterranean while the fifth, Teredus cylindricus (Olivier) is a predatory species found in hollow oaks in association with Anobiidae or Lassius brunneus ants.  Both Oxylaemus species are specialists of ancient forest: indeed, O. cylindricus has not been found in Britain since the 19^th century and may well be extinct here.

Just two British species, formerly placed in separate families: Biphyllus lunatus (Fabricius) in Nitulidae and Diplocoelus fagi (Chevrolat) in Cryptophagidae.  Both are woodland species, B. lunatus can be found in King Alfred’s cakes fungi (Daldinia concentrica), particularly on ash, while D. fagi occurs largely beneath beech bark and on sycamore.

Two species in Britain, both small (3-5mm), light brown hairy beetles: Byturus ochraceus (Scriba) and the slightly smaller B. tomentosus (De Geer).  The latter is a common pest of raspberries and other cane fruits: adults eat the leaves and larvae eat the flower buds and developing fruit.

This family is mainly tropical or subtropical in distribution and has only eight British members.  Small to medium-sized (3-6mm) elongate-oval beetles, most are red-orange and black, although Triplax spp. are metallic blue.  Fungal-feeders, members of this group can be found beneath fungoid bark or in fungi on trees, particularly bracket fungi.  Most species are largely nocturnal.

A large family, with 103 British members.  Generally small to medium (1-11mm) elongate-oval beetles often associated with fungi and decaying organic matter.  There are two subfamilies in Britain, containing approximately equal numbers of species.

Largely associated with fungi, Cryptophaginae are nevertheless found in a wide range of habitats.  Cryptophagus micaceus Rey and several Antherophagus spp. are associated with the nests of tree-dwelling Hymenoptera and bumblebees respectively; other species can be found in rotting bracket fungi, beneath loose bark or in compost heaps.  Several members of genus Cryptophagus are synanthropic and found in stored products.

Ootypus globosus (Waltl) is found mainly in the dung of large herbivores, but most of the rest of the Atomariinae can be found in damp areas with decaying vegetation, particularly marshy areas.  Hypocoprinus latridioides Motschulsky is another dung specialist, but has not been found in Britain since the early 20^th century.

A family with 15 species on the 2012 British list although Mark Telfer has added a 16^th, Olibrus norvegicus Münster, more recently.  A family of small (1.5-3mm) oval beetles, almost hemispherical in shape with a smooth, shining, domed upper surface and a flat underside, reminiscent of a ladybird but smaller and duller in colouration, mostly black or brown.  Many of the species are widespread across southern England, and can often be seen on flowers during the summer, particularly yellow flowers where they are usually found alongside Meligethes spp. (Nitulidae).

A small family with 11 British members.  Most are black or reddish-brown in colour, elongate and somewhat dorso-ventrally flattened.  Several are predatory beneath bark, while others are synanthropic and can be economically-important pests of stored grains (particularly Cryptolestes spp.).

Two species in Britain, Pediacus depressus (Herbst) and P. dermestoides (Fabricius).  Both are small (3.5-4.5mm) red-brown beetles, dorso-ventrally flattened as an adaptation to life beneath bark on a range of trees in various states of decay.  Pediacus dermestoides is widespread across southern England while P. depressus is a rare species with only a scattering of recent records.

A family of 12 elongate species in Britain, 2-7mm long and often dorso-ventrally flattened as an adaptation to life beneath bark.  Largely predatory, several species (Uleiota, Dendrophagus and Silvanus spp.) are primarily found beneath tree bark while the remaining species are mostly found in stored produce or vegetable refuse.  Consequently many of these species (particularly Cryptamorpha and Cathartus spp.) are regularly imported on stored foodstuffs.