Nalassus laevioctostriatus (Goeze, 1777)
Widespread across western and central Europe from Portugal to Greece and north into southern Sweden and the UK although it is absent from most Baltic countries, and in Asia known only from Turkey. In the UK it is locally common and often abundant across Wales and England north to the Humber and sporadic and rare further north into southern Scotland and Northern Ireland; in England it is most frequent in the southeast below London while in Wales it is mostly coastal. The typical habitat is old established deciduous woodland or wooded pasture with a range of trees in various stages of decay but they also occur at the base of heather etc. on sandy or peaty heathland and under debris on exposed cliffs and high ground. In wooded situations the adults are usually associated with oak or, rarely, birch or horse chestnut and a few other trees although in upland and moorland sites they have also been recorded from various conifers, most specimens are brachypterous but they have been recorded from flight-interception traps and so at least some are capable of dispersion by flight, they are crepuscular and nocturnal and spend much of their time grazing algae and lichens (pleurococcus algae are quoted in the literature) on trunks and branches, often in large numbers, and during the day they rest under loose and dry bark, sometimes in small groups. Adults occur year-round, they are active over a long season and overwinter under bark or debris, among those overwintering under bark mortality seems to be high as dead adults which have been infested with a white fungus are generally very common. Mating has been observed over a long season from February into early summer and larvae are known to develop among decaying wood or in organic-rich soil near the base of trees or around heather, they may be abundant and occur in numbers and are sometimes found under logs or stones. Adults are conspicuous and easily observed at night on trunks etc. and sometimes occur in numbers at sap.
Nalassus laevioctostriatus 1
Nalassus laevioctostriatus 2
Nalassus laevioctostriatus 3
6.5-12mm. Elongate, convex and entirely dark brown, sometimes with a weak metallic reflection, superficially similar to various ground beetles but easily distinguished by the tarsal formula, entire dorsal surface glabrous, shiny and finely punctured, the head more densely, so than the pronotum and the elytra. Head transverse with large emarginate eyes that are only narrowly visible from above, vertex and frons smooth and only weakly convex, the clypeus evenly rounded in front of the eyes and covering the antennal insertions, the labrum discontinuous in outline; with several small anterior projections. Terminal maxillary palpomere securiform in both sexes. Antennae long and filiform; reaching back beyond the pronotal base, with all segments elongate; the third much longer than the second. Pronotum transverse, widest near the base and evenly curved laterally to indistinct anterior angles and rounded, near-perpendicular posterior angles, anterior margin smoothly curved, posterior margin sinuate, surface smoothly convex but for two generally distinct basal depressions. Elytra broadest about the middle and evenly curved from the shoulders to a slightly produced apical margin, each with eight complete, finely impressed and punctured striae and a short scutellary striole which often consists of just a few punctures. Legs long and robust with broad femora which are widely visible in normal setting, tibiae gently expanded to truncate apices and with a tiny, hardly noticeable, apical spur. Tarsi 5-5-4; basal pro-and mesotarsomeres broad and densely pubescent ventrally in the male, basal segments of all tarsi similar in width and lacking dense ventral pubescence in the female.