Lymexylon navale (Linnaeus, 1758)

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POLYPHAGA Emery, 1886

LYMEXYLOIDEA Fleming, 1821

LYMEXYLIDAE Fleming, 1821

LYMEXYLINAE Fleming, 1821

LYMEXYLON Fabricius, 1775

This is the classic ‘ship-timber beetle’, a widespread European and Asian species that is occasionally recorded throughout the world from imported timber. Across most of its range it is very local and generally uncommon but it was formerly a very serious pest across much of northern Europe, destroying structural timber generally and ship’s timbers in particular, the adults sometimes swarming around docks in the evening and infected wood teeming with larvae, but today it is rarely a more than a nuisance. In the U.K. it is a local insect of south-central England and the midlands although the adults, while swept from hedgerows etc. are mostly nocturnal and rather elusive and so probably under-recorded. The typical habitat is open deciduous woodland or wooded parkland etc where mature oaks are present in various stages of decay. Adults occur from May until August and are crepuscular and nocturnal; they fly readily and run rapidly over fallen timber etc. although on very hot days they may appear on flowers or foliage among hedgerows or along wooded borders. Females are constantly active, they move rapidly searching fallen or standing timber for suitable oviposition sites, either on old trunks or cut stumps and logs etc. but always where the bark has been damaged or removed and the exposed xylem has become dry. Oviposition occurs from the end of May until July, eggs are laid in groups of 5-15 in wood crevices or old scolytid holes etc. and the freshly emerged larvae bore directly into the xylem, producing very narrow and long tunnels which may follow the annual rings, as they grow they widen these tunnels and may bore short galleries perpendicular to the main tunnel. Older tunnels tend to become blocked with dust and frass and then the larva works its way back to the origin. Fully grown larvae construct a pupal chamber just below the surface and pupate in the spring. Larval borings usually look clean and devoid of fungi, except sometimes for secondary infections, and it is thought the larvae may digest cellulose directly, without pre-digestion from tunnel-borne fungal enzymes. Development may take one or two years.

This species is superficially similar to Elateroides dermestoides, which occurs in similar habitats, but may be distinguished using the characters on the family page.

7-16mm Very elongate, parallel-sided and soft-bodied with several abdominal segments exposed. Male head, pronotum and elytra extensively darkened, female head and elytra laterally and towards the apex darkened. Head proportionally small, widest across large, convex and distinctly pubescent eyes, temples short and strongly constricted to a distinct neck, fronto-clypeal suture absent but there is usually a transverse impression. Antennae long and filiform or weakly serrate in the female, dark with various basal segments pale, inserted in front of and below the eyes beneath a small and prominent ridge; first segment elongate and constricted at the base, second short and broad, and 3-10 elongate, the terminal segment pyriform. Maxillary palpi greatly developed in the male. Pronotum quadrate with distinct posterior angles and sinuate basal margin, the lateral margins lack borders and there is usually a short longitudinal impression medially towards the base. Pronotal surface finely and sparsely punctured and pubescent. Elytra long and smooth, without structure or impressions, the surface punctation and pubescence fine, diverging towards the apex and separately rounded. Legs entirely pale; long and slender, the femora weakly thickened and the tibiae long and parallel-sided or nearly so. Tarsi 5-segmented; the segments not lobed. Hind-wings fully developed and usually visible beyond the elytral apex.

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