Leiopus nebulosus (Linnaeus, 1758)
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POLYPHAGA Emery, 1886
CHRYSOMELOIDEA Latreille, 1802
LAMIINAE Latreille, 1825
ACANTHOCININI Blanchard, 1845
Leiopus Audinet-Serville, 1835
This species is generally common across the entire Palaearctic region, it is common from lowland to alpine altitudes in Europe and extends north into the UK and to central provinces of Fennoscandia, to the south it is present on many of the Mediterranean islands and it extends through the Near East but is absent from North Africa, and in the Caucasus mountains it is represented by the endemic subspecies L. n. caucasicus Ganglbauer, 1887. Adults are active from late May or June until August, peaking in abundance during June and July, they occur in deciduous woodland and wooded parkland generally but may also be found on individual trees in hedgerows or on waste ground etc, they are widely polyphagous and have been recorded breeding in more than twenty species including elm. Beech, hornbeam, alder, hawthorn, sycamore, cherry, oak and chestnut as well as various conifers such as pine and various spruces; in many northern European areas the species is abundant and shows a general preference for oak and hornbeam. Unlike many longhorn species it does not visit flowers although adults are diurnal and often fly during warm sunny days, otherwise they are rather inconspicuous and remain on trunks or fallen timber where they are cryptic and will need to be searched for carefully. Mating occurs throughout the season and females oviposit during the day among the bark or in fissures close to bark on dead or decaying trunks, stumps or fallen timber, and often on quite slender branches. Larvae develop under bark, producing longitudinal galleries that only superficially enter the xylem, and most are fully grown after the first winter, they construct an elongate and flat cell under the bark from wood fragments and pupate during March or April and adults eclose within a few weeks but they do not emerge from the wood until late in May. Adults may be sampled by careful searching, they will usually occur in numbers and often the first sign of their presence is when one lands on the net or on clothing, late morning and afternoons on warm sunny days are best as this is when they are most active, they rarely fly above a meter or two and with a little experience are easily spotted in flight.
5.0-10.0 mm. Very distinctive among our UK fauna, suggestive of Acanthocinus but always with considerably shorter antennae. A sibling species, L. linnei Wallin, Nylander and Kvamme, 2009 has recently been discovered in the UK. Its status is unclear, though it is probably widespread in the south of England, and the two are difficult to separate, some pointers are given below but reference should be made to the original description which includes a thorough account of the morphological differences, this can be accessed HERE.
A small elongate-oval and robust species with very variable but always distinct pale and dark grey patterned and finely pubescent body. Head hypognathous with long slender eyes that curve around the antennal insertions and short diverging temples, vertex and frons weakly convex and densely punctured and pubescent throughout, colour variable but usually extensively dark with a pale median longitudinal line, antennae long and slender, bicoloured but variable in extent, base of segments pale, apices dark; length sexually dimorphic, at least four segments reaching beyond the elytral apex in the male but at most three in the female. Pronotum transverse, moderately strongly but sparsely punctured, densely pubescent, this mostly dark but with weakly-defined paler streaks or patches, lateral margins with a strong backwardly-produced tooth in the basal half. Elytra elongate, about 2.3X longer than wide, with broad, rounded shoulders and gently narrowed in the apical half to separately rounded apical margins, strongly and sparsely punctured throughout, the pattern usually consists of a pale background with variously-formed darker transverse bands in the basal and apical half and numerous dark spots. Legs robust and relatively short, femora strongly broadened medially, tibiae only weakly expanded from the base and all tarsi pseudotetramerous, entirely dark with the middle of the tibiae and often the base of the tarsi pale.
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Our two species differ broadly as follows:
-Pronotal punctation diffuse and finer, pubescence without strongly-delimited dark and pale areas. Frons less convex and narrower, 0.8-1.1 mm between the eyes. Median lobe curved or obtusely-angled apically, spermatheca slender and less strongly curved.
L. nebulosus
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-Pronotal punctation stronger, denser towards the middle, pubescence forming well-defined spots or sometimes a weakly-defined median longitudinal band. Frons more convex and broader, 1.07-1.39 mm. between the eyes. Median lobe acutely angled apically, spermatheca broader and more strongly curved.
L. linnei