TROGOSSITIDAE | uk beetles

TROGOSSITIDAE Latreille, 1802

Bark-Gnawing Beetles

Includes a few local and generally rare species associated with woodland, and a single rarely encountered species which is a pest of stored products.

POLYPHAGA Emery, 1886

CLEROIDEA Latreille, 1802

2.7-11mm

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Around the World

A large family of around 600 described species divided among 3 subfamilies and about 50 genera although the classification is far from settled and there are many more species awaiting description. The group has a worldwide distribution and is particularly speciose in the Southern Hemisphere tropics, with nearly half the described species occurring in South America. Diversity falls away with latitude; around 60 species occur in the Nearctic, with only 22 from Canada. Around 40 species occur in Australia. They are, in general, forest insects that live under bark, in decaying wood or bracket fungi. They fall into two broad ecological groups; Peltinae, Calitinae and Lophoceratinae feed on fungi and occur under bark or within fruiting bodies of polypores etc., and the Trogossitinae which are predators occurring under bark and in galleries of bark beetles. Tenebroides mauritanicus (Linnaeus, 1758) is an exception, occurring as a pest of stored foodstuffs etc., usually inside but also, at least in Europe, occasionally in the wild. The following classification, based partly on Kolibac, 2013, is not comprehensive but will give an idea of the extent of the family.

Lophocaterinae Crowson, 1964.

Includes the Lophocaterini Crowson, 1964, with 14 species in 6 genera of which 8 species in 4 genera occur in the U.S.A. It is sometimes considered to be a subfamily of the Peltinae. Includes a single species known to have occurred in the U.K - Lophocateres pusillus (Klug, 1832).

Peltinae Latreille, 1806.

Includes the Pelini with more than 60 species in 26 genera and 6 tribes. The Thymalini, with 15 species in 7 genera, occur mostly in the Southern Hemisphere although the genus Thymalus Latreille, 1802, with 9 species, has a Holarctic distribution. Includes the genera Ostoma Laicharting, 1781 and Thymalus Latreille, 1802 which are represented in the U.K.

Trogossitinae Latreille, 1802.

Includes more than 330 species in 30 genera and 5 tribes with a worldwide distribution, although 2 tribes are confined to the southern Hemisphere. The tribe Trogossitini Latreille, 1802 includes Nemozoma Latreille, 1804 and Tenebroides Piller & Mitterpacher, 1783, both of which are represented in the U.K. Two genera, Tenebroides and Temnoscheila Westwood, 1830, are particularly diverse, each with more than 100 species.

Trogossitidae are very diverse in form and structure and so are difficult to define for the purpose of identification; the best way of becoming familiar with the group is to examine specimens or google pictures of the various forms, even the very limited U.K. fauna will give an idea of the diversity. In some strange way the rather abstract form of the group, even on a world basis, becomes distinctive with a little experience.

For a more detailed overview of the family click HERE.

Description

The size varies greatly; 1-35mm, although most species are between 8 and 15mm and a few tropical forms reach 50mm. General habitus is diverse; most Peltinae are wide and flattened, most Trogossitinae are elongate and parallel, and most Lophoceratinae are elongate, broad and weakly convex. Trogossitids are usually glabrous or only sparsely pubescent but there are exceptions and some have conspicuous tufts of setae or scales e.g. google the amazing Southeast Asian and Australian genus Lepidopteryx Hope, 1840 (Peltinae), or Trichocateres fascicolifer. Overall the family contains many distinctively patterned species and, especially in the neotropics, many deeply coloured and metallic species. Species of the oriental genus Xenoglena Reitter, 1876 resemble buprestids; they run and fly rapidly around fallen timber hunting for other saproxylic insects. The head is usually visible from above but many species of Thymalini (the Rentonium group which occur among leaf litter etc. in Australia and America) are able to roll into a ball, somewhat reminiscent of a large Abraeus (Histeridae). The anterior margin of the frons varies from being truncate to deeply divided, as in Nemozoma. The eyes are generally entire or, rarely, divided by a canthus. Antennae 8-11 segmented with a conspicuous 1-3 segmented club or gradually thickened towards the apex. Pronotum usually transverse, although elongate in some Trodossitinae, with the lateral margins bordered or denticulate. Elytra generally with regularly punctured striae and often with conspicuously raised longitudinal carinae. Wings usually present and well developed in both sexes. Trocanters triangular. Tibiae often with series of spines along the outer edges, the apex with one or more spurs. Tarsi 5-5-5, or 4-4-5 as the first segment may be partially fused with the second, but the suture is always obvious. 1-4 without lobes, 5 generally as long as the rest combined. Claws large and smooth, without a basal tooth. Empodium varies in size but is usually obvious; projecting and bisetose. Abdomen with 5 or 6 visible ventrites.

A key to the British species can be found HERE.