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Rabocerus gabrieli (Gerhardt, 1901)






POLYPHAGA Emery, 1886

TENEBRIONOIDEA Latreille, 1802



Rabocerus Mulsant, 1859

This Western Palaearctic species has a rather patchy European distribution; it  occurs from the Pyrenees to Northern Italy, Switzerland and Ukraine in the south and north to the UK and well beyond the Arctic Circle in Fennoscandia, it is absent from the Balkans and Asia Minor and the eastward extent of the distribution is parts of European Russia. The species is generally very local and uncommon with only a few records from most northern European countries. In the UK it is widespread across southern and eastern England and there are a few records from the Scottish Highlands, it was formerly recorded from Ireland but is now thought to be extinct there, it is considered very local and uncommon but adults are nocturnal and cryptic and so the species may be under-recorded. Typical habitats are open deciduous woodland and wooded parkland with plenty of mature trees in various stages of decay; adults are generally associated with bark on dead trees and fallen timber or on decaying areas on otherwise healthy trees. A wide range of host trees have been recorded but most records are from oaks (Quercus L.), beech (Fagus L.), birch (Betula Roth.) and, especially, various alders (Alnus incana (L.) and A. glutinosa (L.) Adults are very seasonal; they appear in numbers during March and April and again during October and November but only very occasionally at other times although they are thought to overwinter. Both adults and larvae are thought to be predatory on other subcortical insects etc., and breeding very probably occurs in the spring as larvae have been recorded during the summer from bark beetle galleries (Dryocoetes alni (Georg, 1856) under alder bark on the continent. Sampling involves careful searching as adults are active on trunks and branches during the evening or at night, they may easily be mistaken for small carabids; they usually occur in small numbers and often on thin branches with areas of decaying bark. They are fully-winged but have not been recorded at light or sap.

Rabocerus gabrieli 1

Rabocerus gabrieli 1

© Lech Borowiec

Rabocerus gabrieli 2

Rabocerus gabrieli 2

© U.Schmidt

3.0-4.0mm. Elongate, flat and discontinuous in outline, body shiny and without microsculpture, dark metallic bronze, antennal bases and mandibles pale brown, legs brown, usually with darker femora. Glabrous except for a few extremely fine pale setae scattered across the elytra. Head quadrate; broadest across convex and protruding eyes and with moderately long temples and cheeks, clypeus strongly converging and finely margined in front of the eyes and widely expanded beyond the antennal insertions, labrum quadrate and narrowed to a rounded anterior margin. Surface of head moderately strongly and densely punctured throughout. Antennae inserted laterally in front of the eyes, 11-segmented with segments 6-11 slightly broader and usually darker than the basal segments. Pronotum transverse, broadest in front of the middle and narrowed to obscure anterior angles and obtuse posterior angles, apical and basal margins finely bordered. Pronotal surface uneven; distinctly impressed sub-laterally, vaguely impressed across the disc and with a pair of oblique impressions behind the middle but these are variable. Scutellum slightly elongate, parallel sided from the base then laterally emarginate before a rounded apical margin, punctures across the base a little weaker than those on the pronotum. Elytra elongate, slightly dilated from rounded shoulders to a continuous apical margin, each with seven or eight punctured but not impressed striae that are distinct in places but mostly confused across the base, surface transversely impressed across the basal quarter or third, otherwise smoothly and weakly convex. Legs long and slender with all femora unmodified and of the same width. Tibiae only parallel-sided or only slightly widened from the base, without tubercles or teeth etc. and without obvious apical spurs. Tarsi 5-5-4, the basal and terminal segment of each elongate, and the third segment bilobed but narrow. Claws smooth and with a weakly developed basal tooth. There are no obvious differences between the sexes.

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