LATRIDIIDAE Erichson, 1842
This family includes saproxylic species as well as more general fungus-feeders. Other species occur in a wide variety of habitats, while some infest stored products.
POLYPHAGA Emery, 1886
CUCUJOIDEA Latreille, 1802
This group includes more than 1100 species in about 35 genera and 2 subfamilies, and a further subfamily, Tetrameropsinae Kirejtshuk & Azar, 2008 is known only from Cretaceous Lebanese amber. They are all small beetles and, superficially at least, morphologically not very diverse, the greatest diversity is in northern temperate regions but the group is cosmopolitan due partly to some species of several genera e.g. Cartodere Thomson, C.G., 1859, Latridius Herbst, 1793, Corticaria Marsham, 1802 and Melanophthalma Motschulsky, 1866 being transported internationally with the trade in foods etc., and worldwide more than 35 species are considered to be pests of a wide range of stored products. While the family was first described in 1829 by Curtis as Corticariidae, the more generally known and accepted name has been retained for the sake of stability. Historically various classifications have been used based on the tribes Latridiini, Corticarini, Merophysiinae and Dasyceriini, in 1955 Crowson promoted the first 2 to subfamily status and the others to full families, and since that time the Latridiidae has been divided into 2 subfamilies while the Merophysiidae has been incorporated as a subfamily of the Endomychidae and the Dasyceridae a subfamily of the Staphylinidae. Many minor taxonomic changes have occurred over recent decades, often at the generic level and often involving well-known names so that without up to-date-date literature they can be confusing e.g. the genus Latridius Herbst, 1793 has been partly split among Cartodere Thomson, C.G., 1859, Stephostethus LeConte, 1878 and Thes Semenov Tian-Shansky, 1910, several Enicmus Thomson, C.G., 1859 are now included in Latridius and some Cartodere are now Dienerella Reitter, 1911, and at the generic level many species await to be placed unambiguously. But despite being a speciose family of small and often rather nondescript beetles there has been much recent interest in the group and there is a good deal of modern literature regarding the European fauna. The family is by far most diverse in the Holarctic region; about 140 species of 16 genera
occur in the Nearctic of which 55 are recorded from Canada and the European fauna includes about 190 species of which more than 70 occur in central and northern regions. By comparison only 11 species are recorded from North Africa and about 55 from the whole of Africa, the Australian fauna includes more than 50 species and 3 are known from New Zealand. About 25 have been recorded from Central America and around 65 are recorded from the Neotropical region. Many genera are widespread and there are very few island endemics, the monotypic Besuchetia Dajoz, 1975 being a good example, likewise compared to many other families there are few localized genera; Eufallia Muttkowski, 1910 with 4 species from Australasia, and the Brazilian monotypic Nalpaumia Perris, 1976 are examples. Among the larger and generally widespread genera of the Corticariinae are Corticaria Marsham, 1802, the largest genus of the family with more than 160 species, Corticarina Reitter, 1881 with more than 140 species and Melanophthalma Motschulsky, 1866 with about 130 species, and of the Latridiinae, Cartodere Thomson, C.G., 1859, Dienerella Reitter, 1911, Metophthalmoides Dajoz, 1967 and Metophthalmus Motschulsky, 1850, all with about 40 species, and Enicmus Thomson, C.G., 1859 with about 50 species.
In the wild many species are associated with a wide variety of open and wooded environments where there is plenty of decomposing vegetation. Adults occur on flowers or among herbaceous plants, on trees and among decomposing wood, leaf-litter in most damp situations and in bird, mammal and hymenoptera nests including those of ants and termites. Most are associated with various fungi; Phycomycetes, Deuteromycetes and Ascomycetes, and species of some general e.g. Enicmus feed on the spores of Myxomycetes. Species of several genera have become associated with stored products where both adults and larvae feed on fungal spores that develop in damp conditions, among the best known of these are Cartodere, Corticaria, Corticarina, Dienerella, Enicmus, Latridius and Thes, but despite their economic importance and the roles they play in saproxylic food-chains the life-histories of only very few species have been studied. Pest species develop by grazing surface fungi and so do not damage stored food directly but their droppings may discolour food and they may transport moulds within or between storage areas so accelerating or spreading decay but all species are readily dealt with by maintaining a low moisture content. In domestic situations they may be more difficult to remove as any mouldy surface may host them, and these are likely to be hidden or dark places such as behind appliances, in cellars or larders. Some species e.g. Thes bergrothi and Cartodere nodifer are known to develop on just about any organic material that will support the growth of mould, from paper paste to clothing material, damp books, carelessly stored clothes or mould forming around damp windows and of course foods of any kind. Adults are generally more common during the mild and more damp seasons although some arboreal and flower frequenting species may be common through the spring and summer and at least some will be found among vegetation samples at any time. Decaying compost and fungi can host very large populations, and many are active nocturnally on wood in the vicinity of fungi. In warm weather many are attracted to light and they may occur in numbers, both of individuals and species, in flight interception traps. So far as is known both larvae and adults of all species feed exclusively on fungi.
Adults are small, from less than 1mm to about 3mm, the largest members are among the genus Stephostethus LeConte, 1878, elongate to elongate-oval with the forebody generally narrower than the elytra, and most are rather drab, black to brown and cryptic in nature. The two subfamilies are morphologically distinct and readily distinguished; species of Corticariinae are pubescent, generally very finely so with recumbent hairs, lack prominent dorsal structure although pronotum usually has a median basal fovea or a sub-basal transverse groove and the lateral margins are often serrate, species of Latridiinae are glabrous or, occasionally, have erect setae, the head, pronotum and elytra often have longitudinal carinae, grooves or tubercles and the pronotal margin is usually smooth. Many species of Latridiinae also have waxy secretions to various parts of the body that appear as lateral membranes. The following description applies to the family generally. Head transverse to quadrate, often with a distinct, sometimes modified, neck and, in Latridiinae, often produced broadly in front of the eyes; vertex smooth to variously punctured and sculptured, often with a transverse impression or ridge near the base and/or oblique or curved supra-orbital impressions. Labrum well-sclerotized and usually at least partly visible from above, generally short and narrower than the clypeus but sometimes characteristically broad and curving around it e.g. in Adistemia Fall, 1899, Revelieria Perris, 1869 and Cartodere Thomson, C.G., 1859. Eyes glabrous and very variable; almost flat to very convex and protuberant, sometimes poorly developed e.g. in the cosmopolitan Adistemia watsoni (Wollaston, 1871) with a few large and convex translucent facets. Mandibles variable; from smooth and sharply-pointed to toothed internally and bi- or multi-dentate or lobed apically. Labial palpi 2- or 3-segmented, maxillary palpi 4-segmented, in each case the terminal segment is cylindrical to fusiform. Antennae, inserted laterally on the frons in front of the eyes, thin and usually relatively long; 11-segmented, sometimes 10-segmented e.g. in Migneuxia Jacquelin du Val, 1859, the basal segment usually enlarged and always with a 2- or 3-segmented club. Pronotum usually wider than the head, transverse to elongate and rounded, in Latridiinae often constricted in the basal half, smooth laterally and variously sculptured, in Corticariinae with basal impressions and toothed laterally, sometimes strongly so e.g. in the European Corticaria antonioi Otero, López & Rücker, 2013 with a series of sharp teeth each with a long apical seta, and in the Palaearctic C. serrata (Paykull, 1798) with prominent sharp teeth along the entire margin, sometimes the margin is almost smooth and there is a distinct tooth at the posterior angle e.g. Cortinicara gibbosa (Herbst, 1793). In most cases the surface is smoothly convex but in some e.g. Enicmus Thomson, C.G., 1859) or Dienerella Reitter, 1911 (Latridiinae) the margins are explanate or explanate with a raised lateral border. Prosternum short to long in front of round to oval and contiguous or narrowly separate coxal cavities which are open or closed posteriorly, prosternal process present and sometimes overlaying the mesosternum though sometimes diminutive, mesosternum short, sometimes distinctly notched posteriorly or with ridges between the round coxal cavities, metasternum long, wide and usually convex, sometimes produced anteriorly and emarginate posteriorly to receive the produced basal abdominal sternite, surface generally smooth and punctured. Meta-coxal cavities transverse, sometimes only weakly so e.g. Dienerella Reitter, 1911, and separate, usually widely so e.g. in Dienerella or Melanophthalma Motschulsky, 1866. The scutellum is generally small but distinct and level with the elytra, in some cases almost vertically oriented and not visible from above, the surface smooth or with various ridges which may be diagnostic for various genera. Elytra completely covering the abdomen except in some Melanophthalma, weakly convex and continuously rounded or separately produced apically. Shoulders simply rounded to prominent, lateral margins smooth or dentate, rounded or almost parallel-sided and sometimes explanate. Always with distinct punctured striae although these may be confused as the interstitial punctures may be very large, interstices sometimes modified with carinae, furrows or raised longitudinal tubercles. In most Corticariinae they are finely pubescent but the striae or interstices are often marked by rows of longer erect setae. Hind wings usually well-developed but sometimes missing e.g. in some Cartodere or Adistemia. Abdomen with 5 or 6 free and visible sternites; the basal sternite sometimes with femoral lines near the meta-coxae e.g. in Melanophthalma. Pro-coxae generally conical, prominent and closely approximated or contiguous, meso-coxae convex but less prominent and more widely separated. Meta-coxae transverse, rather flat and usually widely separated. Legs slender and relatively long and generally without prominent teeth or spurs. Tarsi formula 3-3-3 but in some genera the males are 2-3-3 or 2-2-3, usually with all segments simple or only narrowly expanded apically. Claws simple; without lobes, except in the Australian Rethusus Broun, 1886, or appendages and simply pointed or, rarely, bifid.
The larvae are elongate and cylindrical or nearly so with a distinct head visible from above; most have 4 or 4 ocelli on each side but in some groups they are rudimentary and no more than pigment spots, the antennae are 3-segmented, generally with the second longer than 1 and 3, and the mandibles are symmetrical and uni- or multi-dentate. The epicranial suture diverges anteriorly and the stem is variable in length, sometimes absent, and the clypeus is smooth, without a frontoclypeal suture. The labium is distinct and well-developed and the palps are 2-segmented. The legs are 5-segmented and relatively long. The abdomen lacks urogomphi and the spiracles are situated in the pleural membrane.
Enicmus testaceus larva
The UK fauna is representative of the family as a whole and includes members of some of the larger genera as well as some of the widespread pest species, some of which have become established in the wild while others occur only among imports. The Latridiinae includes 8 genera and about 30 species while the Corticariinae includes 5 genera and about 28 species. Compared with many other families only very few species have been recorded as non-established accidental imports. Our species occur in a wide range of habitats and should soon appear by general sampling; decaying vegetation and fungi especially will host species; Cartodere nodifer (Westwood, 1839) may occur anywhere, including among dung which is unusual for the family, and several others e.g. C. bifasciata (Reitter, 1877), Enicmus histrio Joy & Tomlin, 1910 and E. transversus (Olivier, 1790), Dienerella ruficollis (Marsham, 1802) and Corticaria elongata (Gyllenhal, 1927) are common and will soon be found. Cortinicara gibbosa (Herbst, 1793) may occur in abundance on Crataegus blossom and remain common through the spring and summer on flowers and foliage generally, Corticarina minuta (Fabricius, 1792), C. similata (Gyllenhal, 1827) and Stephostethus lardarius (DeGeer, 1775) may also occur on foliage generally while some species e.g. Corticaria rubripes Mannerheim, 1844 occur on conifer foliage. Slime moulds may host species in any habitat and some occur beneath bark or among litter, especially where this is permanently damp; riparian habitats and saltmarshes host their own particular faunas. Among those occurring only indoors are Thes bergrothi (Reitter, 1880), Cartodere constricta (Gyllenhal, 1827), Lithostygnus serripennis Broun, 1914 and Adistemia watsoni (Wollaston, 1871). The near-cosmopolitan stored-product pest Migneauxia lederi Reitter, 1875 was added to our list in 2007