PYTHIDAE Solier, 1834

Log Bark Beetles

Represented by a single species in the UK.

Pytho depressus is a distinctive local species generally confined to coniferous woodland in northern Scotland.

POLYPHAGA Emery, 1886

TENEBRIONOIDAE Latreille, 1802

Pytho Latreille, 1796 

P. depressus (Linnaeus, 1767) 

7-16mm

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Around the World

The Pythidae is a very difficult family to define; species have previously been included in other families e.g. Salpingidae, or species formerly included are now classified in other families e.g. Mycteridae, Salpingidae or Scraptiidae. It is now generally considered to include about 50 species in 6 genera and 3 subfamilies, of which only the Pythinae Blanchard, 1845 occurs in the Holarctic region, the others are to be found in Central and South America, Australia and New Zealand. The problematic species Trimitomerus riversii Horn is included as it seems to be the closest related group but it is unique in that the antennae are sexually dimorphic; in those of the male the last 3 segments are greatly elongated and specialized. The genus Ichyomius Chevrolat includes about 10 species of Neotropical saproxylic beetles that occur on palm and banana trees. The single species of Sphalma Horn, 1872, S. quadricollis Horn, 1872 occurs in North America and Canada. It is a small species, around 6mm, elongate and randomly punctured throughout, superficially resembling a Rhizophagus species.  It occurs under bark on logs and fallen timber. The genus Priognathus LeConte, 1850 is also monotypic; P. manilicornis (Randal, 1838) is native to the Nearctic and occurs in coniferous forests north to the tree-line, it lives under bark and among decaying sapwood on conifer logs. Adults are drab brown and resemble large Salpingids. The 3 species of Osphyoplesius Winkler, 1915 are Palaearctic with single species from Greece, Crimea and one recently discovered (2015) from Sicily. Again this genus is tentatively placed; it was originally included in the Tenebrionidae and then later transferred to the Boridae. They are small beetles that live in the ground or among litter. The species from Greece and Crimea are described from single specimens and have not been found since. The genus Pytho Latreille, 1796 is Holarctic occurring north to the tree-line. It contains 9 species of which 4 are Nearctic. They are relatively large beetles, 9-16mm that live mostly on the wood of conifers. Most are entirely dark and to some extent metallic but the Nearctic species P. seidlitzi Blair, 1925 is attractively dark with pale red appendages. The family is represented in central and northern Europe by 2 species of Pytho.

Description

They are all elongate and moderately convex to flattened and wide beetles which are generally broadened posteriorly. Most are medium sized, 7-17mm. Drab coloured; dark brown or bicoloured with combinations of brown, red and black. Many are to some extent metallic. Dorsal surface often with a fine decumbent pubescence. The head is produced in front of prominent eyes and the temples are usually long. The mandibles are well developed. Antennae 11-segmented and slightly broadened towards the apex, the last segment is usually elongate. The terminal segment of the palpi are generally hatchet-shaped and sometimes truncate. Elytra convex or flattened; punctured or, generally in the flattened species, with striae which are evanescent towards the base. Pronotum smooth and punctured, or flattened with distinct impressions. The legs are long and slender, especially the tarsi. The tarsi may be simple or have the penultimate and sometimes the preceding segment lobed beneath. Formula 5-5-4. The elongate and flattened larvae resemble those of pyrochroids. Both adults and larvae occur beneath bark, the larvae are variously reported as predatory, xylophagous or detritivores.

Pytho depressus (Linnaeus, 1767)

This typical member of the genus occurs from the Pyrenees east through central and northern Europe and through northern Asia. Records are particularly numerous through Scandinavia.  In 2004 it was discovered in Korea. In the U.K. it is very local in pine forests in the Scottish Highlands. Both adults and larvae occur under bark on standing pine trees and logs while on the continent it is also occasionally found on other conifer species and also rarely on broadleaf species. Adults appear early in the year but other than by searching under bark they are rarely seen, they are active nocturnally and are easily overlooked. Among the U.K. fauna the species is distinctive; it is large, 7-16mm, flat and glabrous. The ground colour is brown and the dorsal surface is variously darkened, the colour varies from violet or blue to green with the elytra iridescent metallic. Immature adults are brown or red with a metallic lustre.

Head quadrate, strongly and sparsely punctured, flat on the vertex and raised between prominent eyes. Mandibles robust and toothed at the apex. Antennae filiform; segments 1-7 elongate, 8-10 quadrate, and 11 tapering to a point. Pronotum transverse and widest behind the rounded front angles, widely depressed either side of the middle. Surface sparsely and quite strongly punctured. Anterior margin with fine yellow pubescence. Elytra randomly punctured and mostly glabrous, with well developed shoulders and side margins which become explanate from the basal third. Striae strongly raised and evanescent towards the base and apex. Dilated in apical two-thirds. Colour varies but usually brown at the base and pale laterally. Fully winged. Legs pale with the femora darker. Tarsi 5-5-4. Claws weakly toothed at the base.

The other central European species, P. abieticola Sahlberg, 1875, is smaller at 8-10mm and black above. It is a very rare beetle of undisturbed mountain forests.

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