Octotemnus glabriculus (Gyllenhal, 1827)
Quoted by Joy as common without any regional qualification. There are recent records scattered throughout England with most from the southeast, a single west country record (north Devon) and seemingly absent from Wales. There only a few Scottish records; Dumfries and Galloway and the western and northern Highlands (NBN). No doubt under recorded. A common and usually abundant species throughout our Watford area, we have recorded adults in abundance from every month. Associated with fungal fruiting bodies on a variety of broadleaved timber, locally those of Coriolus (=Trametes) versicolor will almost always host the beetles (along with other Ciids) and often in large numbers e.g a sample of this fungus from Cassiobury park on 17/6/07 produced 328 adults after extraction. Coriolus is typically found on Fagus (Beech) in just about any situation e.g. town centre gardens, either around damaged bark or on cut surfaces of stumps and logs butr we have also found fruiting bodies on Prunus avium (Bird cherry) logs in Whippendell wood and on Quercus (Oak) logs and a Fraxinus (Ash) stump in Cassiobury park, in each case hosting the beetles. They also occur in other species of fungus, we have recorded them from unidentified species on Aesculus (Horse Chestnut), Fagus, Salix, Quercus and Acer platomoides (Maple), and Alexander quotes the fungus Pseudotrametes gibbosa. Beetles found between November and late May are usually brown, sometimes very light, while from June onwards they are darker brown to black. Examining samples of fungus in the field with a hand lens will rarely reveal the beetles, sieving samples of fungus over a white sheet may produce them, especially in hot weather, but heat extraction techniques often produce adults in abundance from apparently barren material.

Although at first Octotemnus seems impossibly nondescript they soon become familiar with a hand lens even in the field; smooth and somewaht shiny, the elongate and very convex form, narrowed anteriorly and broadly rounded posteriorly, are distinctive.

1.5-2mm. The only British Ciid with 8 segmented antennae; yellow with segments 1 and 2 large, 3 elongate and as long as 4 and 5 together, 4 and 5 quadrate and then a dark, pubescent 3 segmented club. Body, when mature, entirely dark brown to black. Head and thorax finely punctured and microsculptured (obvious at X50). Elytra more strongly shining. Eyes prominent, hemispherical and protruding. Head with oblique ridge from front margin of eyes to labrum, covering antennal insertions. Pronotum highly arched and finely bordered. Elytra finely bordered, more strongly so around humeral angles and terminating above a small but obvious humeral prominence. Punctate throughout, usually obscurely so towards base which may appear strigose, with some sparse outstandng white setae in apical quarter. Legs yellow, outer margin of tibiae with small spines. Tarsal segments 1-3 small with long white setae, 4th longer than 1-3 combined. Each tarsus with 2 simple claws.

Description from 10 Watford specimens at X50


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