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Oxylaemus Erichson, 1845






POLYPHAGA Emery, 1886

CUCUJOIDEA Latreille, 1802

BOTHRIDERIDAE Erichson, 1845

TEREDINAE Seidlitz, 1888

O. cylindricus (Creutzer in Panzer, 176)

O. variolosus (Dufour, 1843)

Includes four species of small saproxylic beetles; two occur in Europe and two in North America. The European species are very local and generally rare though widespread and both occur in the UK. Of the Nearctic species, O. americanus LeConte, 1863 is widespread in the east while O. californicus Crotch, 1874 is western, occurring from British Columbia to California. European species are mostly associated with mature broadleaf trees, especially oaks, while the Nearctic species are associated with various conifers. The biology is largely unknown but adults are generally active over a short season during the summer and are often found in association with ants or wood-boring beetles, the European species sometimes occur in flight-interception traps and are sometimes found in large numbers in subterranean pitfall traps. Larvae are thought to be predatory but it seems more likely they are mycophagous and commensal in the galleries of wood-borers or developing on underground moulds and spores etc. Both European species are likely to be in decline and under-recorded.

They are small, 2.8-3.8 mm, elongate and cylindrical, shiny black to dark brown with extremely fine setae to the head, pronotum and elytra. Head deflexed and rather flattened, smoothly convex and evenly punctured between weakly convex eyes, temples long and converging but usually retracted into the thorax, frontoclypeal suture well-impressed, labrum transverse and truncate or weakly sinuate apically. Antennae inserted laterally in front of the eyes, the insertions visible from above, 11-segmented with a flat and rounded one-segmented club divided into a pubescent apical part and glabrous (but for the usual setae) basal part. Pronotum elongate, parallel-sided in front of the middle and narrowing to obtuse posterior angles, apical margin curved from rounded anterior angles, lateral margin finely bordered throughout, surface strongly punctured throughout or with a central longitudinal strip unpunctured or at least more sparsely so. Pronotal base with four deep fovea; a more-or-less round impression either side of the centre and a variable elongate impression from the base beside each lateral margin. Elytra parallel-sided from angled and slightly produced shoulders to a continuous apical margin, basal margin smoothly curved and unbordered, each with nine more-or-less complete striae and an abbreviated stria between the fifth and sixth, all  consisting of rows of strong punctures. Scutellum small, transverse and curved laterally. Elytral interstices flat or weakly convex, without ridges, depressions or punctures. Legs short and robust. Femora unarmed. Tibiae broadened from the base and truncate apically, all with at least some small external teeth and two spurs at the inner apical angle. Tarsi with four simple segments in both sexes. Claws smooth and without a basal tooth. Among our UK fauna these might be confused with Teredus or Rhizophagus, both of which lack the pronotal impressions.  Our species can be distinguished as follows:

Oxylaemus variolosus

Oxylaemus variolosus

Oxylaemus cylindricus

Oxylaemus cylindricus

-Pronotal surface more-or-less evenly punctured throughout, external basal furrows extending forward to about one-third the pronotal length. Elytra narrower (W: L 0.42-0.48) and more parallel-sided, striae less strongly punctured. 2.8-3.4 mm.

O. cylindricus

-Pronotal surface smooth, or at least very sparsely punctured along a central strip, external basal furrow extending to about the middle. Elytra broader (W: L 0.52-0.54) and (slightly) less parallel-sided, striae more strongly punctured. 3.0-3.8 mm.

O. variolosus

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