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Orchestes rusci (Herbst, 1795)







POLYPHAGA Emery, 1886

CURCULIONOIDEA Latreille, 1802

CURCULIONIDAE Latreille, 1802

CURCULIONINAE Latreille, 1802

RHAMPHINI Rafinesque, 1815

Orchestes Illiger, 1798

Locally common in Europe from the Pyrenees to Italy and Romania and north to the UK and central provinces of Fennoscandia, otherwise known from most of the Palaearctic region to the far east of Russia and Japan, this species is common throughout most of England and Wales and rather less so in Scotland and Northern Ireland. The species is associated with various birches (Betula L.); most often with European White Birch (B. verrucosa Ehrh.) and Downy Birch (B. pubescens Ehrh.) but also others including Silver Birch (B. pendula Roth.) Typical habitats are open deciduous woodland and wooded margins where the hosts are common but they also occur on young trees on heathland, moorland, parks, gardens and wetland margins. Adults overwinter and are active from May until September, peaking in abundance during June and July, the species is thought to be univoltine in northern regions but two generations each year are sometimes quoted in European works. Mating occurs in spring and summer following a period of maturation feeding, and females chew into the apical margin of leaves to lay a single egg although two eggs may be laid, one either side of the apex. Larvae mine along the outer margin of the leaf to about the middle and then turn in towards the centre of the leaf, producing a characteristic sinuate mine that gradually widens along the length. The mine is then widened to an almost perfectly circular area, often beside the central vein, where the larva will pupate. This disc is usually between 5 and 20 mm wide and the larva will bind the upper and lower leaf surfaces tightly together, it is mostly excised so that it falls to the ground but in rare cases it will remain on the leaf. Adults eclose from July, overlapping with the previous generation, but they will not reproduce until the following year. Adults may be found by sweeping host foliage, especially on saplings and young trees in open situations, they are diurnal and usually occur in numbers though they jump powerfully and sampling can be difficult.

Orchestes rusci

Orchestes rusci

2.2-2.5 mm. Broadly oval with a relatively small forebody, body black with a distinct pattern of white or creamy scales; rather sparse on the head, pronotum and across the elytral base, and on the elytra forming a dense strip along the sutural interstice behind the scutellum and two irregular transverse bands, across the middle and before the apex, antennae pale reddish, legs black with pale tarsi.  From above the head consists mostly of the large and slightly oval eyes which form the outline, the interocular distance being very narrow, and the weakly curved (though strongly down-curved) rostrum is held under the head and thorax and so is not usually visible. Rostrum thickened at the antennal insertions; towards the middle in females, further from the base in males. Antennae 11-segmented with 6-segmented funiculus and elongate and pointed club, basal segment distinctly longer than the scape. Pronotum transverse, broadest towards the base and narrowed to rounded anterior angles, basal margin slightly produced medially, surface evenly convex and moderately strongly and densely punctured throughout. Pronotal margin without outstanding long setae. Elytra elongate (about 1.3X longer than wide) and smoothly curved from rounded shoulders to a continuous apical margin, striae shallow and strongly punctured, interstices weakly convex and roughly sculptured. Front and middle femora not toothed ventrally, hind femora greatly enlarged and smooth (without a line of tubercles) along the ventral surface. Claws free and toothed at the base.

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