Euophryum confine (Broun, 1881)
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POLYPHAGA Emery, 1886
CURCULIONOIDEA Latreille, 1802
PENTARTHRINI Lacordaire, 1865
EUOPHRYUM Broun, 1909
Native to the north island of New Zealand this small saproxylic weevil was first recorded in the U.K. in 1937 and over the following few decades it spread rapidly through the Home Counties, now it is common throughout England and Wales, including Anglesey and Man, and there are records scattered through Scotland and Northern Ireland. Soon after it became established in the U.K. it began to occur in Europe and it is now widespread through western and central regions, in 1980 it was detected in Canada and is now widespread, extending into the United States. The species occurs in damp decaying timber of a wide range of deciduous and coniferous trees, adults occur year-round and may form large aggregations in the spring and summer; their emergence is synchronized and so they may appear suddenly in abundance and at such times they can be swept from foliage close to suitable host material and although they fly are rarely seen to do so. Adults may be expected from almost any habitat where suitable host material occurs, they will not infest solid and dry wood but are strongly attracted to volatiles released by various fungi that infest damp wood e.g. Coniophora puteana DC (1815) (wet-rot fungus), Serpula lacrymans P.Karst (1884) (dry rot) or Fibroporia vaillantii (DC) Parmasto (1968) white pore fungus, and for this reason they will attack stored timber or wood left in gardens etc. as well as wood products such as cardboard, books and plywood, and they are common in buildings where structural timber contacts the soil or damp walls, very large infestations may build up and are often detected by the presence of dead beetles below windows or doors. Adults may also be attracted to dry wood that has previously been infested with fungi, and wood with a moisture content as low as 20% is a viable host for the larvae, these feed on hemicelluloses and cellulose and excrete lignin in their distinctive ellipsoid and coarse frass. Females lay eggs in cracks and crevices or may bore into the host material to do so, and larvae feed just below the surface forming long and straight galleries along the grain which often break the surface. Adults bore similar galleries and, as they may live for up to 16 months, all stages may be present together in a single host sample, especially
in heated premises. Larvae emerge from the eggs after 2 or 3 weeks, generally in late spring or early summer although inside this may vary widely, and take up to 10 months to become fully grown. Pupation occurs within the wood etc, generally between June and October, the adults eclose after 2 or 3 weeks and other than when dispersing and mating they spend much of their time tunnelling through the host material. Adult emergence holes are small and usually irregularly oval with jagged edges and they may occur in great numbers as they usually emerge en masse.
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These are small and rather nondescript weevils that are likely to be overlooked; 2.5-3.6mm and entirely dark brown or with the legs and a humeral spot lighter. Head widest at convex and protruding eyes, coarsely punctured from the posterior margin of the eyes forward. Rostrum broad, produced forward and narrowed between the base and the antennal insertions, with coarse punctures that become finer towards the apex. Scrobes lateral and not visible from above, antennae inserted about half way along the rostrum; scape short and broadened towards the apex, funiculus 5-segmented, the club 3-segmented and pointed. Pronotum elongate and a little wider than the elytra; broadest behind the middle and smoothly curved laterally to a strong constriction behind the anterior margin. Scutellum small and triangular with the base in line with the elytral base. Elytra parallel-sided and continuously curved around the apex, completely covering the abdomen, with strongly impressed and punctured striae, and convex and finely and sparsely punctured interstices; the ninth interstice is strongly raised around the apex so that the margin appears explanate from above. Legs short and robust with thickened femora and short, almost straight, tibiae; the external margin of the pro-tibia is produced to an evenly rounded and incurved sharp tooth; the internal margin has a much smaller apical tooth. Tarsi 5-segmented, with the basal segments lobed and the terminal segment long and curved.
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The combination of the 5-segmented funiculus and raised ninth interstice will identify our Euophryum species; the superficially similar Pentarthrum huttoni Wollaston, 1854 lacks this last feature while E. rufum (Broun, 1881), also an invasive New Zealand native, has rounded antennal clubs and the rostrum excised at the base of the scrobes, in E. confine the rostrum is smooth around the base of the scrobes.