POLYPHAGA Emery, 1886
TENEBRIONOIDEA Latreille, 1802
MELANDRYIDAE Leach, 1815
False Darkling Beetles
A very varied group, most likely to be encountered by chance amongst decaying timber. Considerable experience will be needed to become familiar with this family.
As with some other families of the tenenbrionoidea the limits of the Melandryidae vary but, as often classified by modern standards, and as considered here, about 450 species are included in 60 genera and 3 subfamilies. Some tribes, e.g. Osphyini Seidlitz, 1898, are often treated as sub-families. They are small to medium sized beetles, 2-20mm and vary from oval and rather flat to slender, convex and elongate. The majority are elongate and rather nondescript insects; either entirely drab or some shade of brown with transverse markings to the elytra. The upper surface is often very finely pubescent. Head with or without distinct temples, and often retracted into the thorax e.g. in Orchesia Latreille, 1808 or Serropalpus Hellenius, 1786. Antennae 11-segmented and filiform, serrate or moderately expanded towards the apex, the insertions are not hidden from above-a character which will separate the family from the Tenebrionidae. The palpi are usually prominent and often have the terminal segment securiform. Mandibles bidentate or bilobed at the apex. The form of the pronotum varies; in most cases it is broadest at the base and tapered towards the apex, often without distinct front angles, in the genus Osphya Illiger, 1807 it is broadest near the middle. In most cases the only surface sculpture is the basal fovea, otherwise variously punctured. There are usually, except in some Melandryinae, more or less distinct lateral keels. The scutellum, except in some Melandryinae, is conspicuous. The elytra are always elongate and completely cover the abdomen, acuminate e.g. Orchesia, broad and dilated towards the apex e.g. Melandrya Fabricius, 1801, or parallel and continuously or separately rounded at the apex e.g. Osphya. Legs long and slender, in Osphya the metafemora are dimorphic, being expanded in the male. Tarsi 5-5-4 (in all U.K. species) or 4-4-4; all segments visible and often with some bilobed. Generally fully winged; most species are capable of strong flight. Abdomen with 5 visible sternites. Some species vary considerably in size.
All species are saproxylic, living on dead or damaged wood both as larvae and adults. The adults are generally fast moving, cryptic and fly well. The majority of species live in and around bark crevices, under loose bark, in decaying wood or in fungi. The majority of species are nocturnal and, while a few adults will sometimes visit flowers in bright sunshine, in general members of the family are seldom seen. The larvae of most species live within the dead wood of stumps or fallen timber and feed on invasive fungi although a few species feed directly in the fruiting bodies of tree fungi. Most of the larvae are cylindrical and elongate, sometimes slightly flattened, and usually weakly sclerotized. The head and thorax is often darkened, and urogomphi may or may not be present. About 40 species occur in central Europe.
Around the World
By far the smaller of the two subfamilies, the Osphyinae Seidlitz, 1898 includes 4 genera. The genus Brasilium Pic, 1917 includes 6 species endemic to Brazil. The single species of Falsoconopalpus Pic, 1917, F. obscures Pic, 1917 is also Neotropical. Conopalpus Gyllenhal, 1810 includes 3 species of which 2 occur in Europe, the type species C. testaceus (Olivier, 1790) being the only U.K. representative. Osphya Illiger, 1807 contains about 25 species typified by our only U.K. representative O. bipunctata (Fabricius, 1775). The genus occurs throughout the Holarctic as well as the Middle East and Central America.
The remaining species, about 90% of the world fauna, are classified in the subfamily Melandryinae Leach, 1815. This subfamily has a worldwide distribution and while the U.K. fauna includes only 15 species it is typical of much of the subfamily. The following list deals only with the U.K. genera.
The genus Hypulus Paykull, 1798 includes about 10 species and has a Holarctic distribution with 2 from North America and 3 from Japan. The greatest diversity is in Asia. The single species H. quercinus (Quensel, 1790) occurs in the U.K. and is typical; elongate and rather flat with the pronotal base narrower than the elytra across the shoulders, the elytra lack striae. Colouration in the genus is generally pale with various darker transverse fascia to the elytra. Most species occur in broadleaved woodland.
The genus Zilora Mulsant, 1856 includes 8 species and is Holarctic; 5 species occur in the Nearctic region. Typified by the U.K. species Z. ferruginea (Paykull, 1798), they are drab brown to black insects with distinctly punctured elytra that lack striae. All inhabit coniferous forests.
As many as 6 subgenera of the genus Melandrya Fabricius, 1801 are recognized , several of which are sometimes considered to be distinct genera, and so it includes 20 or 30 species depending upon how it is defined. The genus is Holarctic with the greatest diversity in East Asia. The 2 U.K. species typify the genus although some eastern members are bicoloured; black with brilliant shiny blue metallic elytra. They are all associated with decaying timber in old woodland.
The genus Orchesia Latreille, 1807 is a large and widely distributed genus including about 60 species in 3 subgenera. Only 3 species occur in the Nearctic, and the greatest diversity is in the Eurasian region but they are also well represented in Australia, New Zealand and Central and South America. The 3 U.K. species typify the genus; long-oval and drab, and often with transverse pale red or orange fascia to the elytra. They may be recognized by the very long metatibial spurs. The pronotum is transverse and generally as wide as the elytral base, rounded anteriorly and without front angles. They usually have well developed basal fovea. They are fast moving and elusive insects associated with decaying timber in wooded habitats.
Of the 7 species included in the mostly Palaearctic genus Abdera Stephens, 1832, 5 occur in the U.K. Two species occur in the Nearctic region. They are similar to Orchesia but lack the long hind tibial spurs. All are small species <4.5mm and drab, usually with transverse markings to the elytra. They occur in broadleaved woodland, generally under bark or among fungi.
The genus Xylita Pic, 1798 includes 4 species, of which the Holarctic X. laevigata (Hellenius, 1786) occurs in the U.K. Two species occur in the United States and one in Chile. They are medium sized beetles, 6-10mm elongate and parallel sided, drab; generally with the head and pronotum darker than the elytra, or vaguely patterned. The pronotum is smooth, without basal fovea, and the elytra lack striae.
The genus Phloiotrya Stephens, 1832 includes about 35 species in 2 subgenera. It is very widely distributed; Holarctic and extending south to Australia and South America. They are typical elongate and parallel melandryids; drab with the upper side distinctly punctured, the pronotum with, or lacking basal fovea and the elytra with obsolete longitudinal costae. The head is usually hidden from above and the eyes are large and entire. Some species vary considerably in size e.g. the single U.K. species, P. vaudoueri Mulsant, 1856 ranges from 6-14mm. Most species occur in broadleaved woodland.
The genus Anisoxya Mulsant, 1856 includes 7 species and is mostly Palaearctic with some extending to Asia and Japan, and only one occurring in The Nearctic region. A single very widespread species, A. fuscula (Illiger, 1798) occurs in the U.K. They are small, <4mm and drab coloured insects, distinctly pubescent and with the head visible from above. The legs are long and the beetles can move very rapidly among bark and logs making them very elusive and difficult to record.
A key to the British species can be found HERE.
Although the U.K. fauna includes only 17 species, some of these are members of large and widely distributed genera, coupled with the fact that many of the genera are superficially similar, a familiarity with the U.K. species will provide a reasonable insight into the wider world fauna.
The following characters will define the U.K. species: 2.5-16mm. Body elongate broad or, generally, slender and tapering. Head never rostrate, temples present; usually small and gradually narrowed behind the eyes, without a narrow neck. Genae never expanded over the antennal insertions. Antennae filiform and sometimes widened but never clubbed. Pronotum with a distinct side margin, at least at the base. Prosternal process indistinct and usually very small. Tarsi 5-5-4. Claws never pectinate. The following brief description is intended to place the U.K. fauna into a wider context; at the time of writing (2016) the family contained only the species listed above; in the past it has included various others e.g. the Tetratomid genus Hallomenus Panzer, 1793.