Platyrhinus resinosus (Scopoli, 1763)

Resin Weevil

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POLYPHAGA Emery, 1886

CURCULIONOIDEA Latreille, 1802

ANTHRIBIDAE Billberg, 1820

ANTHRIBINAE Billberg, 1820

PLATYRHININI Bedel, 1882 

PLATYRHINUS Clairville, 1798

In the UK this species is classified as nationally scarce (B) but there appears to have been an increase in both range and abundance over recent years and this is probably no longer appropriate. It is locally common across south and central England and South Wales in wooded habitats, including parkland and gardens, and is associated with the fungus Daldinia concentrica which develops primarily on Fraxinus (ash) but also occasionally beech and other broadleaf trees. Adults have a long season, we have recorded them in January, persisting into late summer or autumn and are both diurnal and nocturnal, they can often be found active or at rest during the day on fallen timber or logs etc. but may be cryptic to the inexperienced eye as they resemble bird droppings. Mating occurs throughout the spring and eggs are laid from late spring into the summer, several eggs are laid directly into the fruiting body which will host the larvae until they bore into the underlying wood to complete their development over one or two years; fully grown larvae construct pupal chambers in the wood during late summer or autumn but resulting adults remain in their chambers until the following year. The wider distribution includes the whole of Europe north to the Arctic Circle in Scandinavia, northwest Africa, Iran, Israel, Ukraine etc. and east into western Siberia. On the continent it is locally common and appears on a wider range of fungi e.g. in Scandinavia mainly on Hypoxylon fragiforme, which occurs mainly on Fagus (beech) but also on other broadleaf trees, H. multiforme (mainly on birch) and H. fuscum (birches) as well as Daldinia concentrica, in northern areas mostly on Daldinia loculata which develops on fire-damaged birch and it has been recorded from other species e.g. Ustulina deusta (develops on a wide range of broadleaf trees) and Fomes fomentarius (mostly on birch in the north, more catholic in southern areas).

This large and distinctive weevil might only be confused with the similarly large Platystomos albinus but is readily distinguished by the presence of an incomplete transverse sub-basal pronotal keel, with a little experience both are immediately recognized. 7-15mm. Elongate and discontinuous in outline with a ‘lumpy’ appearance, black or reddish-brown with dense recumbent pubescence; extensively pale to the head, rostrum and elytral apices but forming cryptic patterns on the elytra. Head, including rostrum, parallel-sided and slightly elongate with small, convex and prominent eyes and a deep median longitudinal impression. Antennae short and slender with an abrupt 3-segmented club, inserted laterally about mid way along the rostrum. Pronotum transverse, angled laterally and constricted before sharp anterior angles, surface rugose and coarsely punctured; before the base with an incomplete transverse keel. Elytra parallel-sided, with broad and well-defined shoulders and evenly curved to continuously rounded and narrowly explanate apices, striae narrow and consisting of series of shiny punctures which stand out among the dense scales, interstices broad and mostly flat; colour and pattern vary but there are usually series of transverse pale and dark bands, extensively pale apices and several pale markings along the base. Legs robust and rather long, femora and tibiae slender and lacking teeth, tarsi 5-segmented but appearing 4-segmented, fourth segment deeply bilobed, claws toothed at the base.

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