A small family with 11 British members, these are small beetles (2-4mm) which resemble weevils (particularly Salpingus ruficollis (L.)).  They are generally found in association with dead wood (mainly on twigs or beneath bark) where they are active predators of other insects, particularly bark beetle larvae, although Aglenus brunneus (Gyllenhal) is a stored product pest.  

Three medium-sized (9-17mm) bright crimson species in Britain.  Schizotus pectinicornis (L.) is the only species with black on the pronotum and also has very pectinate antennae.  It is also the rarest, found only in the Scottish Highlands (though there is an old record from Herefordshire).  Pyrochroa coccinea (L.) has all-red elytra and pronotum but a black head and a largely southern distribution, while P. serraticornis (Scopoli) is all-red and widespread.

The orange-brown, dorso-ventrally flattened larvae are found beneath bark and can also be identified to species level relatively easily.  The smaller S. pecticornis larvae have strongly curved posterior cerci while those of Pyrochroa are short and straight.  Pyrochroa serraticornis larvae have a raised bar across the enlarged 8^th tergite, near the base, which is absent in P. coccinea.

A single species of Pythidae occurs in Britain: Pytho depressus (L.), a locally-distributed medium-sized (14-15mm) brown-black beetle found under the bark of pine trees in Scotland.  The striate elytra often have a greenish sheen.  Spends at least two years as an orange larvae beneath bark, similar in appearance to larvae of the Pyrochroidae.

One British representative, Mycterus curculioides (Fabricius), a medium-sized (7-9mm) oval beetle found most frequently on flowers.  The overall appearance is reminiscent of an Otiorhynchus weevil, but with grey-gold elytral and pronotal pubescence.  Not recorded in Britain for more than a century and presumed extinct here.

10 species of medium to large (10-35mm) beetles.  They are named after their ability to produce a bitter tasting oil from their knee joints containing the toxin cantharadin. All are nest parasites of solitary bees and are found in a variety of habitats including grasslands, woodlands and gardens.

Three genera occur.

Meloe (8 species) are distinctive black soft-bodied beetles with very short, overlapping wing cases.  Three species Meloe violaceus Marsham, Meloe proscarabaeus Linnaeus and Meloe rugosus Marsham are widespread though local.  Meloe brevicollis Panzer and Meloe mediterraneus Muller are very rare and confined to a few sites.  Three others Meloe autumnalis Linnaeus, Meloe cicatricosus Leach and Meloe variegatus Donovan are thought to be extinct but as two species also thought to be extinct have been found in recent years they may await rediscovery.

Lytta (1 species) very distinctive metallic green beetle known as the Spanish Fly.  Very rare and only known from the Isle of Wight.

Sitaris (1 species) very distinctive orange and black beetle which is a nest parasite of Anthophora bees.  Very rare and currently known from one site in Hampshire.

These beetles have a fascinating life history. The females of Meloe and Lytta dig short burrows in the soil and lay batches of eggs underground.  Sitaris eggs are laid within the hosts nest hole.  Each female may lay several batches totalling several thousand eggs. The newly hatched larvae are known as 'triungulins' as they have three hooks on each foot.  They climb on vegetation and flowers or sit in the hosts burrow and attach themselves to passing insects.  The few that survive are those taken to the nests of the host bees. Once in the nest they feed on the pollen collected by the bee for her own larva and change to a grub-like form in the process. Pupation takes place in the hosts burrow.  Some species remain underground as adults through the winter ready to emerge on the first sunny days of spring.  Adults are diurnal during the spring and summer except Meloe rugosus and Meloe mediterraneus which are winter active and nocturnal.  Adults feed on a variety of vegetation including the leaves and flowers of buttercups (Meloe) and privet (Lytta).  Sitaris adults do not feed.

All species have declined in the last 50 years due to changes in countryside management which has led to the loss of their host bees.

One further species Stenoria analis (Schaum) is known from the Channel Islands and may be found in the near future.  It is a nest parasite of the Ivy Bee Colletes hederae which is a recent colonist.

A family with 10 British representatives, 5-17mm long, many of which are shining metallic blue-green in colour.  The soft, flexible elytra do not meet all the way along the midline, but diverge as each tapers independently to its apex, although this varies from scarely noticeable, as in Ischnomera spp., to diverging close behind the scutellum, as in Oedemera nobilis (Scopoli).

Oedemera lurida (Marsham) and O. nobilis develop as larvae in the stems of herbaceous plants, and can be highly abundant in grassland as adults, particularly on flowers.  Oedemera femoralis (Fabricius) is a locally-distributed large, pale brown, nocturnal species formerly in genus Oncomera, which can be found on ivy blossom or at light between April and September.  The Ischnomera caerulea of older literature is actually a complex of three species: I. caerulea sensu strictu (L.), I. cinerascens Pandellé, and the relatively widespread I. cyanea (Fabricius), which are best split by dissection.

A varied family, with 47 species in Britain.  1.5-25mm long, many are synanthropic, particularly in cellars and stables but also in stored products.  Tenebrio molitor (L.) is the familiar mealworm, sold as food for birds or reptiles while Tribolium spp. are pests of flour and grains in both industrial and domestic situations.  Subfamily Diaperinae are found in fungi and decaying wood or other vegetable matter.  This subfamily includes Diaperis boleti (L.), an attractive orange and black species found in bracket fungi which can be mistaken for a Chrysomelid.

Two species (Myrmechixenus subterraneus Chevrolat and M.vaporariorum Guerin-Meneville) are associated with ants, but both are rare.  Nalassus laevioctostriatus (Goeze) is widespread and common on tree bark after dark.  Several species are largely coastal in distribution, and should be looked for at the bases of plants in dune systems.  Lagria hirta (L.) is an elongate-oval species which can be abundant in mid-summer.  It has mid-brown, hairy elytra and jet-black head, thorax and appendages and can be found on low vegetation or at light.

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.

One species in Britain, the wasp-nest beetle Metoecus paradoxus (L.).  A spectacular beetle, 10-12mm long, with a bright orange abdomen, orange side patches on the pronotum, huge feathered antennae and triangular wedge-shaped translucent elytra which do not entirely cover the flight wings.  Larvae are parasitic in wasp nests, traditionally said to be only found in subterranean nests but several modern records are from nests in roof spaces.  Eggs are laid in the autumn on rotting wood, and larvae hitch a lift on wasps which visit to collect wood scrapings.  Once back at the nest, the larva drops off and finds a part-grown wasp grub, which it parasitizes and eats before emerging as an adult in mid-summer.

The 2012 checklist gives 17 British species of Mordellidae, but this is a taxonomically-confused group, with several recent descriptions and synonomisations from the British fauna.  As a group they are distinctive: oval-elongate, pubescent brown or black beetles, 2-9mm long, with an extended, elongate pygidium reminiscent of a sting.  Adults are characteristically found curled in a c-shape on flowers, where they feed on pollen.  When disturbed, their general escape mechanism is to skip about and tumble from the flowers, hence their vernacular name.