Ostoma ferrugineum (Linnaeus, 1758)

With the exception of Southern Europe this species is widely distributed throughout the Palaearctic region extending east through Russia to North Korea and Japan. It is generally common over most of this range but thought to be in decline in central Europe and until recently was thought to be extinct in Denmark. Because of its habitat and lifestyle Ostoma is an elusive species; it was discovered in the U.K. in the mid 1900’s and is now known from the surviving Caledonian forest areas in the Cairngorm National Park north of Inverey. Here the adults occur from April to June or a little later, they are fungivores, occurring under bark on dead trunks of large Pines that are infested with the bracket fungus Phaeolus schweinitzii. The larvae feed on decaying wood and fungi in Scot’s Pine with extensive rotten xylem infested with Phaeolus or Fomitopsis pinicola. In Europe they are known from a wide range of trees and their feeding habits are more diverse; in Hungary they occur in beech forests and in Spain under the bark of conifers in high altitude forests where they feed on wood boring insects. In Ukraine the larvae have been recorded from Pinus, Picea, Betula, Populus tremula and Tilia, and adults have been found in fruiting bodies of Pycnoporellus fulgens, Fomitopsis pinicola and Gleophyllus Sp. from May to August. Here the life cycle takes two years with both adults and larvae overwintering. Adult emergence holes are semi-circular.  In the U.K. it is listed in the Red Data Book (Shirt, 1987) as endangered. In Germany, where it is rare, it is considered as endangered but across Europe generally it is listed as of least concern. They fly and have been recorded at light.

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7-10mm. A broadly oval species; parallel sided and from above suggestive of a Cassida. Overall dark brown with pale margins and appendages. Pronotum and elytra with broad explanate margins. Head densely punctured and slightly narrowed in front of the convex eyes. Antennae 11 segmented with a 3 segmented club. Pronotum densely punctured, less so on disc. Sides evenly rounded from obtuse hind angles to rounded front angles which project strongly in front of the apical margin. Basal margin widely sinuate. Scutellum wide and punctured. Elytra very convex across the middle and steeply declined to the explanate margin. Odd numbered striae raised to apical declivity, with a row of fine setae. Even numbered striae not raised, smooth. Interstices with raised transverse ridges which alternate with strong punctures; one row either side of each stria. Epipleura wide and pubescent to apex. Front tibiae with a robust, hooked apical spur on the inside. Mid and hind tibiae with two tiny apical spurs. Tarsi 5-5-5, without lobed segments; last segment longer than the others combined. Claws strongly curved with a sharp angle at the base which does not quite form a tooth. Empodia short and stout, with two very long apical setae at apex.