CORYLOPHIDAE LeConte, 1852
These tiny beetles are associated with a variety of decaying organic matter in many different habitats, and are often found in extraction samples. In warm weather they can also be found by general sweeping.
POLYPHAGA Emery, 1886
CUCUJOIDEA Latreille, 1802
This is a small family of about 400 species included in 27 genera and 2 subfamilies although several classifications will be found in the literature; the UK fauna has long been classified into 2 subfamilies which are now considered to be tribes of a recently-defined Corylophinae LeConte, 1852, and historically the group has been rather widely dispersed, it was originally included within the Coccinellidae and several genera have recently been transferred from the Latridiidae and Endomychidae.
The common name refers to form of the pronotum which is produced anteriorly in many species and so covers or at least partly covers the head, and their minute size; members of this family are among the smallest of all the insects and among the coleoptera only some species of the family Ptilidae Erichson, 1845 are smaller. The majority of species are between 0.5 and 2.0mm, some few extend to 2.5mm and some of the Periptyctinae can measure 3.5mm. Most are drab black to pale brown, a few have contrasting forebody and elytra e.g. some Holopsis or Sericoderus, and some have paler margins or maculae to the pronotum and/or elytra e.g. some Microstagetus or Corylophus, and Stanus bowesteadi Ślipinski et al., 2009 is unusual in having a distinct pattern to the elytra but the only striking species are found among the Australian Periptyctus which otherwise rather strongly resemble endomychids. The habitus varies widely from elongate and discontinuous e.g. Foadia, to virtually circular and continuous in outline e.g. in some Holopsis, and from flattened and widely explanate e.g. Cleidostethus to very convex dorsally as in Holopsis, which might easily be mistaken for a coccinellid, or both dorsally and ventrally as in Orthoperus. Most species are very finely punctured dorsally, lack elytral striae and are finely to rather densely pubescent although there are several genera with entirely glabrous species e.g. Orthoperus or Clypastraea. Identification to the generic or specific level may be problematic but fortunately most temperate faunas, and certainly that of
the UK, are restricted and many genera or even species are characteristic and recognizable from gross morphology and for this reason members of the family are not likely to be confused with any others, more especially considering their vary small size. Equally small ptilids are distinct in having the antennae fringed with fine long hairs and the club much more loose and elongate, some tiny cryptophagids e.g. Ephistemus, may be mistaken for the present group but lack the disproportionally large basal antennal segments or are otherwise distinct from overall morphology. A familiarity with the UK fauna will allow many foreign species to be place within the family but more technically the majority conform to the following combination of characters. Size very small, head not prognathous, generally at least partly covered by the pronotum, with quite long antennae bearing a rather compact 3-segmented club and 2 enlarged basal segments, lacking a frontoclypeal suture and with single-lobed maxilla. Elytra variable but leaving at least the pygidium exposed. Pronotum very variable but the prosternal cavities are always closed externally. Legs usually long and slender; pro-coxae close together and often with a distinct prosternal process, meso- and meta-coxae often widely separated, meso-trochanter small and strongly oblique; the femur and coxa in contact, tarsi 4-segmented, without bilobed segments although the third segment may be lobed ventrally.
It is thought that all corylophids are fungivores both as larvae and adults, feeding and developing on hyphae and spores of a wide range of species but mostly Deuteromycetes and Ascomycetes in habitats rich in decaying organic matter e.g. leaf-litter and compost or under bark and among decaying wood. They occur regularly among suitable extraction samples and in the field may be found when sieving organic material in a wide range of situations. In warm weather they disperse by flight and so may be found by general sweeping or beating the stems and foliage of a range of plants, especially in damp places and often in the evening. Traps baited with decaying fungi or fermenting organic matter may also be successful during the warmer months, and bundles of stems tied and left in likely places through the winter may produce adults when examined in the spring. Needless to say their small size necessitates a very careful examination when searching under bark or through sieved material but with a little experience they become obvious e.g. when searching around fungi at night by torchlight they are readily spotted and pootered. Larvae are tiny; <3mm when fully grown, and occur in much the same habitats as the adults; they are generally fusiform and moderately flattened although strongly so in Rypobiini, and lack terminal cerci. They vary from lightly to heavily sclerotized dorsally and are lightly sclerotized and pigmented ventrally. The head bears 2 stommata either side dorsally, 2- or 3-segmented antennae, lacks a frontoclypeal suture and has a distinct suture between the capsule and the labrum. Each thoracic segment has a pair of 5-segmented legs, each with a single claw. The abdomen has 10 visible segments, the anterior segments with a pair of annular spiracles. Most species have normal mouthparts i.e. simple to multidentate mandibles and 2- or 3-segmentd maxillary palps etc. but in Rypobiini they are variously fused to form sucking apparatus.
Our UK fauna includes 11 species although Orthoperus atomarius (Heer, 1841)has not been recorded since the mid twentieth century; it may be rediscovered as it is a synanthropic species associated with old barrels and corks in wine-cellars and has been recorded as adventive in cities on the continent. Our other members of the genus occur in the wild; O. atomus (Gyllenhal, 1808) is widespread in south and central England and south Wales, it occurs in pine woodland among litter and avian nests in tree hollows etc. O. aequalis Sharp, 1885 is widespread in southern and eastern England and south Wales, it occurs in old woodland and wooded parkland, mostly beneath the bark of oak and beech. O. brunnipes (Gyllenhal, 1808) is a local species occurring among decaying vegetation in wetland areas in southern and eastern England. O. corticalis (Redtenbacher, 1849) is a southern species of old deciduous woodland and wooded parkland. O nigrescens Stephens, 1829 is the most widespread member of the genus occurring throughout England and Wales north to the Humber in deciduous woodland and parkland. Rypobius praetermissus Bowestead, 1999 was recorded from coastal West Sussex in 1919 and from coastal Dorset in 1931, these were probably immigrants from the continent where it is often associated with salt marsh and marginal wetland environments. Our two species of Sericoderus Stephens, 1829 are associated with decaying vegetation and fungal fruiting bodies; S. lateralis is our most common member of the family and may occur in a range of open and dry situations, S. brevicornis has only been recognized as British since 2007 and so far seems to be restricted to East Anglia and the midlands. Corylophus cassidoides (Marshan, 1802) is a wetland species occurring across East Anglia but otherwise mostly coastal from the Wash to Anglesey. C. sublaevipennis Jacquelin du Val, 1859 occurs at the at the base of plants in grassland or on cliffs, the majority of records are from coastal areas from the Wash to Dorset.
Although these tiny species are generally unpopular with collectors there is a wealth of information available both in the literature and online, and a very good introduction to the family can be gained from Stanley Bowestead’s 1999 book; A revision of the Corylophidae (Coleoptera) of the West Palaearctic region. For some more up to date information a very good paper is available here Ślipinski et al. (2009) Phylogeny and classification of Corylophidae (Coleoptera: Cucujoidea) with descriptions of new genera and larvae.
Around the World
Periptyctinae Ślipinski et al., is a small subfamily of 3 genera and is restricted to eastern Australia; Periptyctus Blackburn, 1895 includes about 20 species and is widespread, while the monogeneric Pakalukodes Ślipinski et al., 2001 and Weirus Ślipinski et al., 2009 are known only from northern Queensland. Corylophinae includes the majority of species, it is represented in all the zoogeographical regions and some genera are cosmopolitan. The group is divided into 10 tribes, 4 of which are represented in the UK. Foadiini Ślipinski et at., 2001 includes 4 genera and 5 species from Australasia and North America. Cleidostethini Bowstead et al., 2001 includes the single species Cleidostethus meliponae (Arrow, 1929) from East Africa, recently transferred from Coccinellidae. Aenigmaticini Casey, 1900 includes 2 genera; Aenigmaticum Matthews, 1888 with several species in Central and North America, and the monotypic Stanus Ślipinski et al., 2009 from New Zealand. Parmulini Poey, 1845 includes 5 genera and is cosmopolitan. Arthrolips Wollaston, 1854 includes more than 50 species and is Holarctic as well as occurring in Australasia and Central America, both the North American and the European faunas include 8 species but so far none are listed as British although this is likely to change e.g. A. fasciatus (Erichson, 1842), originally described from Tasmania, is spreading throughout the world and has been recorded from France, Italy, Spain and Madeira, and A. croceus Matthews,1887, which occurs among stored products, has been recorded from the UK but is not established. Clypastraea Haldemen, 1842 is a genus of about 20 species occurring throughout the Holarctic as well as the Afrotropical, Neotropical and Oriental regions but is absent from Australasia, several species are widespread and common in across Europe e.g. C. pusilla (Gyllenhal, 1810) occurs throughout, from the Mediterranean to Scandinavia, but so far the genus has not been recorded from the UK. The monogeneric Lepesmella Paulian, 1950 is known only from Central Africa. Peltinodini Paulian, 1950 includes the single genus Holopsis Broun, 1883, the distribution is Holarctic with species also from Australasia, South and Central America and North Africa. Several species are present in Asia and a single flightless species, H. gigas (de Perrin, 1894), occurs in Algeria and Tunisia, but otherwise they are absent from the Palaearctic region. Nine species occur in eastern North America. Teplinini Pakaluk et al., 1994 includes 2 species of the south-western Palaearctic genus Teplinus Pakaluk, Ślipinski & Lawrence, 1994, both are widespread Mediterranean species.
The remaining four tribes are represented among the UK fauna. Orthoperini Jacquelin du Val, 1857 includes the single genus Orthoperus Stephens, 1829. The genus is widely distributed across the Holarctic region and has been recorded from all the major zoogeographical areas; 16 species occur in North America and 11 in Europe of which 6 extend to the UK. Sericoderini Matthews, 1888 includes 2 more or less cosmopolitan genera, they are recorded from all the continents and the greatest diversity is in the Australasian and Pacific regions; it is represented in the Nearctic region by 5 species of the large genus Sericoderus Stephens, 1829, and in the Palaearctic region by 3 species of Sericoderus and 2 species of Aposericoderus Paulian, 1950. In the UK the cosmopolitan Sericoderus lateralis (Gyllenhal, 1827) is our most common and widespread member of the family although it has recently (2007) been found to comprise 2 very similar species and so the distributions may not be fully understood; S. lateralis is widespread through south and central England and Wales whereas S. brevicornis Matthews, A., 1890 seems to be virtually restricted to East Anglia. A third European species, S. pecirkanus Reitter, 1908, occurs only around the Mediterranean. Corylophini LeConte, 1852 includes 3 genera, it is widespread in the Palaearctic and African regions and has also been recorded from New Zealand. Homogrypinus Teitter, 1908 includes 2 African species. Microstagetus Wollaston, 1861 includes 2 species; M. parvulus Wollaston, 1861 is widespread across North Africa and Mediterranean Europe while M. dubius Paulian, 1940 is known only from the Abyssinian highlands. Corylophus Stephens, 1833 occurs throughout the Palaearctic region and is also present in Africa and Australia; 3 species occur in Europe, C. tectiformis Wollaston, 1854 is endemic to Madeira while C. cassidoides (Marsham, 1802) is widespread and extends to the south of the UK and C. sublaevipennis Jacquelin du Val, 1859, which occurs mostly in south western Europe, has been recorded from the coasts around southern England and Wales. Rypobiini Paulian, 1950 includes 4 genera of which 2 are represented in the Palaearctic region; Catoptyx Matthews, 1887 is an Oriental genus, and Hoplicnema Matthews, 1899 is Neotropical. Rypobius LeConte, 1852 is represented in North America by the type species R. marinus LeConte, 1852, an eastern species of coastal environments, and in the Western Palaearctic region by 3 species, 1 of which extend to the UK; the widespread European R. praetermissus Bowestead, 1999 has been recorded from the south coast of England. The Western Palaearctic fauna includes about 50 species and the European fauna 37 species of which 18 occur in central regions e.g. Germany, and 11 extend to the UK, and while our fauna is limited it represents 4 tribes and is representative of much of the wider Corylophinae.