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Orthocis Casey, 1898





POLYPHAGA Emery, 1886

TENEBRIONOIDEA Latreille, 1802

CIIDAE Leach, 1819

O. alni (Gyllenha, 1813)

O. coluber (Abeille de Perrin, 1874)

This mostly Holarctic genus was formerly included as a subgenus of Cis. Estimates vary as to the number of species because many have been reassigned, but present estimates vary between 26 (Catalogue of Life Checklist) and about 70 (Bug guide). The greatest diversity is in the Palaearctic region; 5 species occur in North America, 3 are known from the Neotropical region and several occur in Australia and Mauritius. The European fauna includes 12 species, of which 2 extend to the UK. Typical of the family, all species are associated with various fungi. The biology is not known but both adults and larvae are mycophagous, and the complete development likely occurs among the host tissue. The species are generally locally common or scarce, but adults are often abundant in samples (usually along with other members of the family), and a single undisturbed fungus may host the beetles over many seasons. Adults are fully-winged and can fly but they do not generally appear in flight-interception or light traps. They are nocturnal but only rarely encountered on the surface, and so the best way to sample them is by taking samples either for extraction, or to keep in moderately dry conditions until the fauna emerges.

In general form they are very similar to Cis, but they may be distinguished by the more elongate third antennomere (only slightly longer than the third, and more than half as long as 4-7 combined), and the distinct anterior pronotal angles which are visible when the pronotum is viewed directly from above. They are elongate, convex and rather slender beetles, entirely dark brown to black with very fine, sometimes hardly noticeable, pale pubescence to the pronotum and elytra. The head tends to be more densely and obviously pubescent. Head narrowly visible from above, weakly convex between round and convex eyes, finely and densely punctured and with a distinct frontoclypeal suture. Antennae pale with darker clubs, 10-segmented with a loose 3-segmented club. Clypeus unmodified in males. Pronotum quadrate or nearly so, lateral margins straight or weakly curved and always distinctly bordered, apical margin curved and usually produced forward in both sexes, basal margin straight or bisinuate. Pronotal surface evenly convex, without structure, finely but not densely punctured, and usually rather dull compared with the elytra due to fine microsculpture. Elytra parallel-sided or weakly curved from rounded or obtusely-angled shoulders to a continuous apical margin, smoothly convex and finely punctured throughout.  Tibiae only weakly expanded from the base, apices simply rounded or obliquely truncate and without apical spines. Tarsi 4-segmented; basal segments short and weakly lobed, terminal segment long and expanded from the base. Our UK species may be distinguished as follows (Adapted from Joy’s 1932 handbook):

Orthocis alni 1

Orthocis alni 1

Orthocis coluber 1

Orthocis coluber 1

Orthocis alni 2

Orthocis alni 2

On average larger, 2.5-3.0 mm. Pronotum rounded at sides, and with explanate sides broader  and simple at edges; el. with scales smaller, and punctation finer and more diffuse.

O. alni (Gyllenhal, 1813)

On average larger, 2.0-2.5 mm. Pronotum straight at sides, with explanate sides narrower, edges with scales; el. with scales larger, and punctation larger and less diffuse; L. 2-2.5mm.

O. coluber (Abeille de Perrin, 1874)

Orthocis alni (Gyllenhal, 1813)

Orthocis alni is a widespread Palaearctic species, extending from Europe and Asia Minor to the far east of Siberia; in Europe it is locally common from the Pyrenees to the Balkans, and extends to the far north of Fennoscandia. It is locally common in south-eastern and central England and Wales, but otherwise very local and rare, reaching the far north of Scotland and Northern Ireland. The species is associated with various fungi in broadleaf woodland and wooded parkland etc. Recorded hosts include Stereum rugosum (Pers.) Fr., Exidia glandulosa Bull. Ex Fr. and Auricularia auricula (Hook.) Underw. The list of hosts is likely to be much larger, and the beetle often occurs on old oaks and so any fungus here is worth investigating. Adults are present year-round, they overwinter among host material or among adjacent bark or decaying wood, and are active from March until November, peaking in abundance during May and June, and sometimes again in late summer.

Orthocis coluber (Abelle de Perrin, 1874)

Orthocis coluber has a very restricted Southern and Western European distribution; it tends to be very local and scarce everywhere, and so far is known only from the following countries: France. Austria, Italy, Hungary, Slovakia, Belgium and the UK, and is also recorded from Malta, Sardinia and Sicily. Here it is a very rare species, known only from a few sites in Kent and Sussex. The species is associated with Trametes versicolor (L.) Lloyd (1920), often developing on old oak stumps, but also recorded from willow (Salix L.) and alder (Alnus Mill.). On the continent Adults have been recorded from March until September and most records are from May and July.

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