Nudobius lentus (Gravenhorst, 1806)
This generally common species occurs across the entire Palaearctic region, extending to the far east of Russia, China and Japan; its European distribution is mostly central and northern but there has been a general expansion over recent decades and it has gradually spread south, this expansion occurred in France from the 1960s and the first Spanish record was from Madrid in 2012. Until recently the southern limits of the distribution were the Pyrenees, northern parts of Italy and the Balkans and it occurs sporadically in Asia Minor, while to the north it extends into the UK and Fennoscandia. In 1932 Joy gave the distribution in his handbook as simply Scotland, 4 (by which he meant the north east), and for many years the species occurred only in Scottish pine woods but there was either a gradual southward expansion during the 20th century or it was transplanted across England and Wales with the movement of timber and the expansion of pine plantations, it may also have been imported with timber from the continent but however this occurred it is now widespread and locally common across much of the mainland. The species is saproxylic and associated with various conifers, particularly pines, and to a much lesser extent a few broad leaf trees such as birch, beech and oak when growing in the vicinity of conifers, and it occurs from lowlands to the highest limit of the tree-line throughout much of Europe. Both adults and larvae are predatory, both occur in bark-beetle galleries and the borings of other beetles such as longhorns and bostrichids and adults have been found at sap but they are more generally specialist predators of scolytids and adults frequently occur in pheromone traps for spruce and pine bark beetles. The species is thus regarded as an important control agent in commercial conifer plantations and both adults and larvae are known to predate some of the most injurious species e.g. Hylurgops palliatus (Gyllenhal, 1813), Ips cembrae (Heer, 1836), Pityogenes chalcographus (Linnaeus, 1760) and various species of Tomicus Latreille, 1802. Adults occur year-round under the bark of both standing and fallen timber and will generally be found in numbers over a small area, they mostly occur bark that looks healthy and that might be ignored by the coleopterist but adults also occur under older loose bark and so are easily sampled as the following account shows: ‘Our specimens were found under close fitting but loose bark on the top and sides of a fallen pine trunk, this was extensively excavated with galleries containing abundant adults and small (2-3mm) larvae of Drycoetes autographus (Ratz.) and Hylurgops palliatus and the occasional tiny Elateroides larva. Both scolytids had been present since April 2009, at which time the bark was healthy and difficult to remove, since then the subcortical space had progressively filled with damp black wood pulp and frass from the excavations, and it was among this we found the rove beetles; nineteen specimens were found under about half a square metre of bark, when uncovered they either remain stationary or move slowly towards the nearest debris.
Nudobius lentus 1
Nudobius lentus 2
6.5-8.5mm. An elongate and rather parallel-sided species easily recognized by the colour and form of the pronotum. Head, pronotum and abdomen black, elytra pale reddish-brown to bright red, legs pale red, antennae and palps pale brown. Head elongate with small weakly convex eyes and long parallel temples, posterior angles rounded and basal margin straight, surface with scattered punctures of various sizes, frontal sulci strongly impressed, angled about the centre and extending back to (at least) the hind margin of the eyes. Antennae short and robust, the scape about as long as segments 2-5 combined, segments 4-10 becoming progressively more transverse and the terminal segment elongate-oval. Neck short and slightly rounded laterally, about one third the head width. Pronotum elongate (about 10:7), anterior and posterior angles and margins rounded, lateral margins sinuate about the middle where the marginal bead curves under the anterior margin, surface with fine transverse microsculpture, fine punctures throughout and a series of 7-10 larger punctures in two longitudinal series extending from the anterior to the posterior margins. Elytra about as long as the pronotum, slightly elongate, overlapping along the suture and broadened apically, surface shiny with very fine microsculpture (X50) and random larger punctures which tend to form longitudinal series towards the suture and lateral margins. Abdomen shiny black or dark brown with the terminal segment paler, lateral borders narrow and strongly raised, surface with fine sinuate and transverse microsculpture. Legs long and robust, femora not toothed below, tibiae with stout spines towards the apices and a long spur at the inner apical angle. Tarsi 5-segmented, claws smooth and curved, all with a weak internal tooth near the base.