Barynotus moerens (Fabricius, 1792)
The European distribution of this species is sporadic and restricted to western and central areas; it is generally rare further north to the south of Scandinavia and east towards the Russian border; the most eastern record is from Moscow where a colony was discovered in 1999, representing the only record for that country, and it is a recent established adventive in Canada and the United States. In the UK it is sporadic though locally common across England and Wales although absent from the West Country and rare in the north, extending to the Scottish borders. Throughout much of its range, including the UK, it is probably exclusively parthenogenetic as only females have been found but in some central European countries males occur but only very rarely. The typical habitat is open deciduous woodland and wooded borders with a dense or patchy ground cover of herbaceous plants, adults occur year-round and are generally active on low vegetation from April until late in the summer, through the winter and early spring we have found them in local woodlands among moss and under bark and logs. The usual host is Mercurialis perennis L. (dog’s mercury) and the majority of records are from this plant but they are polyphagous and have been recorded from a broad range of species e.g. the Russian population was from Taraxacum but more generally they are known from Cirsium spp., Ranunculus spp., Viola, Primula, and Lamium maculatum. Adults feed upon foliage while larvae consume roots, populations tend to be small and adults will often occur as single specimens and so they are easily missed; dog’s mercury usually grows densely and extensively in damp shady woodland and so they are easily overlooked by the collector, more especially so as they are flightless and a colony tends to remain static for several years but we have on one occasion found adults in abundance in a small area of local woodland where they were feeding on Mercurialis and oblivious to heavy teeming rain. Localized large populations occur on the continent where, at least in Poland, it is sometimes a serious pest of commercially grown gladiolus. The best way to sample adults is by extensive sweeping in likely habitats although they tend to be conspicuous, at least to the experienced eye, on low vegetation and damaged foliage will be obvious among large populations, but they will also occur in pitfall traps and among extraction samples through the colder seasons.
8-9mm. Dorsal surface usually with dense round, dull brown and bronze metallic scales that form obscure paler stripes or a mottled effect, especially laterally on the elytra, and that mostly obscure the underlying dark cuticle. Head broadest at the base and evenly narrowed to the rostrum, vertex smooth above the eyes and anteriorly with 5 longitudinal furrows that extend onto the rostrum, eyes transversely oval and only weakly convex. Rostrum broad and slightly elongate, with scrobes obvious from above. Antennae brown with the club darker, scape short, curved and abruptly thickened before the apex, funiculus 7-segmented and club elongate, narrow and pointed. Head and pronotum with fine recumbent pale hairs; pronotum transverse, broadest in front of the middle and without lateral borders, the surface coarsely tuberculate with a distinct median longitudinal furrow. Elytra elongate-oval and characteristically angled before the apex, rounded laterally and broadest behind the middle. Striae strongly punctured and generally obvious among the scales, alternate interstices (1, 3, and 5) raised and with 2 or 3 rows of erect pale setae; the fifth strongly raised in the apical third and the sutural interstice raised at the apex. Legs dark, the tibiae and tarsi generally a little lighter, femora and tibiae variously covered with scales, femora without an internal tooth. Pro tibia sinuate internally, more-or-less straight externally and expanded into a tooth at the inner apical angle. Claws free and smooth internally.