TROGIDAE MacLeay, 1819

Skin Beetles

Suborder:      POLYPHAGA Emery, 1886

Superfamily:  SCARABAEOIDEA Latreille, 1802

Genera:         1

Species:        3

Size:              5-12mm

Our three UK species are all rare and very local insects associated with animal detritus in a range of habitats. All are very distinctive and should not be confused with any other group; the key below will allow their identification. 

Around the World

Trogidae is a worldwide family of 3 or 4 (if Afromorgus is considered as a separate genus) genera and about 300 species. They are commonly known as hide beetles or skin beetles but these names more generally apply to the Dermestidae. The large genus Omorgus Erichson, 1847, with around 100 species, occurs mostly in the southern hemisphere; primarily South America and Africa but there are a few species in the United States, Canada, Asia, and North Africa, and 2 species occur in Europe: O. Italicus Reiche, 1853 in Italy, which is also widespread through Asia to India and China, and O. Suberosus (Fabricius, 1775) which occurs through southern Europe as well as Australia and the southern United States south to South America. The genus Polynoncus Burmeister, 1847 includes 32 species from South America, 2 of which are from the Galapagos Islands. Trox Fabricius, 1775 is a large genus of around 160 species with a worldwide distribution including many from Australia, where it is thought the genus may have evolved, but poorly represented in South America. A single species, T. gonoderus Fairmaire, 1901 occurs in Madagascar.

Description

Species of Trogidae range from 2.5 to 20mm and are oblong to short-oval and strongly convex with the underside more or less flat. The colouration is drab; black to shades of brown or grey but in life they tend to be covered with soil or debris from the feeding site and so are cryptic. Exceptions to this are some species of Omorgus e.g. the attractively coloured African O. baccatus (Gerstaeker, 1867) with a red head, pronotum, elytral margins and legs. The entire upper surface is usually pubescent. The head is deflexed and usually not visible from above, being covered by the pronotum. The antennae are short and 10 segmented with a 3 segmented club. The pronotum is usually punctured and characteristically sculptured. The strongly sclerotized elytra are usually deeply striate and often have prominent groups of setae, pits or tubercles over the entire surface. The legs are stout; the tibiae usually have external teeth and a strong terminal spur. Tarsi 5,5,5. Most species have well developed wings and are good fliers. Species of Trox stridulate by rubbing a file-like structure on the lateral margins of the abdominal segments against the inner margins of the elytra.

Ecology

Species of the family generally avoid detection and predation due to their covering of soil or debris and their ability to remain motionless for long periods when disturbed. They tend to be local and rare and found in small numbers. Many species occur in drier and often sandy habitats and some are known regularly from mammal and bird nests where they feed on remains or the regurgitated pellets of raptors. Most feed on dry animal remains; horn, bones, fur, hide and feathers etc. and are often the last species to arrive at a carcass. Conversely, they may be the first to arrive at charred or burned corpses, feeding and exposing fresh tissue that is colonized by other carrion feeders. Females excavate shallow tunnels beneath a food source in which they lay eggs allowing the larvae access to the food. A succession of females may visit a food source over a period of time so that adults and larvae may be found feeding together. When disturbed the larvae retreat into their burrows beneath the food. Adults may occasionally occur away from the host material as they disperse after eclosion e.g. at night on tree trunks after emerging from avian nests in hollows etc. Some species of Trox have been used in museums to clean away dry material left on skeletons. The creamy-white grub-like larvae have a strongly sclerotized head and plate-like covering on the prothorax, the abdominal segments have at least one transverse row of setae and darken with age and accumulated faeces. The antennae are 3 segmented. There are generally 5 larval instars.

UK Species
European Species

T. eversmanni Krynicky, 1832, occurs in central Europe and east to Siberia.

T. sordidatus Balthasar, 1936, is from south-eastern Europe.

T. fabricii Reiche, 1853, is from Spain, Sicily and North Africa.

T. clathratus (Reiche, 1861), is a Corsican endemic.

T. transversus Reiche, 1856, is from Greece, Turkey and Syria.

T. cotodognanensis Compte, 1986, is from Spain.

T. cribrum Gene, 1836, is a Sardinian endemic.

T. strandi Balthasar, 1936, is from Algeria.

T. cricetulus Adam, 1994, recorded from Spain and Croatia.

T. granulipennis Fairmaire, 1852 is from Spain, North Africa and the Middle East.

T. hispidus (Pontoppidan, 1763) occurs locally throughout Europe.

T. klapperichi Pittino, 1983 occurs through Turkey to the Middle East.

T. leonardii Pittino, 1983 occurs in Spain and through North Africa to Israel.

T. litoralis Pittino, 1991 occurs through Southern Europe from Italy to Greece.

T. martini (Reitter, 1892) occurs in North Africa.

T. niger Rossi 1792 is from Eastern Europe.

T. nodulosus Harold, 1872 occurs in Sardinia and Corsica.

T. perlatus (Goeze, 1777) is widespread in Western Europe, including the U.K. to Siberia.

T. sabulosus (Linnaeus, 1758) is widespread in Western Europe, including the U.K.

T. scaber (Linnaeus, 1767) occurs throughout the Holarctic, including the U.K.

Further Reading

A Practical Handbook of British Beetles

Norman H. Joy

Remains valuable, keys specimens to family and species level.

Dung Beetles and Chafers

-RES Handbook

L. Jessop

Keys all British species.

Checklist and bibliography of the Trogidae

Provides distribution and bibliography on all the worlds species.

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