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Triplax scutellaris Charpentier, 1825







POLYPHAGA Emery, 1886

CUCUJOIDEA Latreille, 1802

EROTYLIDAE Latreille, 1802

EROTYLINAE Latreille, 1802

TRITOMINI Curtis, 1834

Triplax Herbst, 1793

Widespread in Europe but very local and generally rare; in southern and central regions it is more-or-less confined to upland and lower mountain woodland and, with the exception of the Pyrenees and the Alps, its presence in many countries is based on only a few records, to the north it remains very rare in the UK, Denmark and the southern Baltic countries but it is locally common an often abundant across Fennoscandia where it reaches the far north. Further east it extends across northern Russia, where it is often common, but the eastern limit of the range is not known. In the UK it is now known from only a very few sites near Newcastle upon Tyne in north east England, it was formerly more widespread across the north but it seems to have declined during the 20th century. The typical habitat is old established broadleaf woodland; adults occur under bark or among various fungi on decaying wood of a wide range of trees; often Aspen (Populus tremula L.), Birch (Betula L.), willows (Salix L.), Elm (Ulmus L.) and Holly (Ilex L.) but also many others, and in Fennoscandia they also occur on individual trees in hedgerows, grassland, wetlands and other open biotopes. The majority of records are from Oyster Mushrooms (Pleurotus (Fr.) P. Kumm, 1871), and, typical of the genus, these are likely to be the main larval host. Adults occur over a long season from March until September; they peak in abundance during June and July but mating probably occurs throughout the season. Little is known of the biology but larvae have been found overwintering among moss at the base of old trees, and teneral adults occur in the spring. It is likely that, at least in the UK, the species is univoltine, the nocturnal adults disperse by flight and have been recorded in flight-interception traps, they tend to occur in numbers and sometimes in abundance, but their dispersal abilities are obviously very limited.

Triplax scutellaris 1

Triplax scutellaris 1

Triplax scutellaris 2

Triplax scutellaris 2

4.5-5.5 mm. Elongate-oval and almost continuous in outline, glabrous, forebody, scutellum, legs and entire underside reddish, elytra shiny black, antennae black with the base reddish, often extensively so. Head flat and densely punctured between convex and prominent eye, clypeus smoothly rounded anteriorly, last maxillary palpomere securiform. Antennae inserted laterally in front of the eyes; 11-segmented with a gradual 3-segmented club. Pronotum transverse, broadest across slightly obtuse posterior angles and narrowed to projecting anterior angles, lateral margins bordered, basal margin produced medially, surface evenly convex and finely punctured throughout, without a transverse groove. Elytra smoothly curved and narrowed from finely-toothed shoulders to a continuous apical margin, basal margin smooth and not, or only very finely, margined, surface evenly convex but for a sub-humeral depression, with distinct punctured striae and wide flat interstices which are randomly punctured, in places almost as strong as the striae. Legs short and robust; femora unarmed, tibiae gradually broadened from the base to obliquely-truncate or emarginate apices, without external spines or obvious apical spurs. Tarsi 5-segmented but appearing four-segmented as the diminutive fourth segment is usually barely visible within the broadly bilobed third segment.

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