Betulapion simile (Kirby, 1811)
Formerly included in the large genus Trichapion Wagner, 1912 this species now represents the monospecific genus Betulapion Ehret, 1994 which is the only member of the subtribe.
This Holarctic species is represented in the United States and Canada by B. s. walshii (Smith, J.B., 1884) and across the Palaearctic region by the nominate subspecies; it is locally common though sporadic throughout Europe except for the south-east, extending from Algeria north to above the Arctic Circle in Scandinavia; in the UK it occurs throughout England and Wales, being most common in the southeast, East Anglia and the midlands and generally absent from the west country and the islands, and it is widespread though local in northeast Scotland. Throughout most of its range the species is oligophagous on various Betula (birches); in North America on B. papyrifera (Marshal), and in the UK on B. pendula Roth. Adults may be found throughout the year, they become active in early or mid-April and feed on developing young foliage for a while before mating and ovipositing begins; eggs are laid in the tips of female catkins and the larvae mine down towards the base, consuming unripe seeds as they go, here they will pupate from early or late June. The pupal stage lasts for about 2 weeks and new-generation adults appear from July, these will remain on the host foliage until September or October and then pass then overwinter. Typical habitats are woodland, wooded parkland and wasteland where the host trees are not too disturbed by people; we have often found them on solitary trees exposed on moors and heathland and on woodland borders, and they seem to prefer small mature trees rather than saplings.
Betulapion simile 1
© Dave Hodges http://thewcg.org.uk/
Betulapion simile 2
© Lech Borowiec http://www.cassidae.uni.wroc.pl/Colpolon/index.htm
Betulapion simile 3
Typical specimens are very distinctive and readily identified and so will help to give an introduction to the family; they are distinguished among the UK species by the entirely dark body which has a bronze-metallic reflection (sometimes faint or, rarely, absent), deep elytral striae and distinct, albeit short, dorsal pubescence and dense fringe of long and pale hairs around the ventral margin of each eye.
1.8-2.4mm. Elongate-oval with distinct shoulders and elytra broadest behind the middle. Head transverse with large convex eyes and scattered pale pubescence which is generally dense around the margins of the eyes, vertex weakly convex with distinct punctures and microsculpture but otherwise smooth. Rostrum long, slender and cylindrical but slightly widened around the antennal insertions; much longer in the female, >1.5X longer than the pronotum, in the male <1.5X longer. Antennae dark or with the base of the scape pale; slender with the scape long and abruptly thickened towards the apex, antennomere 2 longer and wider than 3-8, club broadly elongate and pointed. Pronotum transverse and widest behind the middle, anterior margin narrower than the posterior margin and lateral margins slightly constricted before the base and apex. Surface strongly and quite densely punctured pubescence oblique to the longitudinal axis and the basal fovea linear and short. Scutellum glabrous. Elytra with distinct shoulders and evenly curved laterally, with well-impressed and strongly punctured striae; the first stria abbreviated well before the scutellum, 2-5 reaching the base and 6-7 abbreviated before the humeral callus. Interstices flat or weakly convex, about 2X wider than the striae and finely and irregularly punctured. Hind wings fully developed. Legs long and slender, entirely dark and finely pubescent throughout. Male meso- and meta-tibiae with a spur at the inner apical angle, absent in the female. Males are distinctly more slender and parallel-sided.