Molorchus minor (Linnaeus, 1758)
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POLYPHAGA Emery, 1886
CHRYSOMELOIDEA Latreille, 1802
CERAMBYCINAE Latreille, 1802
MOLORCHINI Gistel, 1848
Molorchus Fabricius, 1792
This is the only European member of a large Holarctic genus of more than one hundred species, the greatest diversity is in the eastern Palaearctic and Oriental regions and only three species are known from North America, it occurs throughout Europe from France north to the UK and reaching the Arctic Circle in Fennoscandia, and extends sporadically east through Asia Minor and Russia to China, Japan and Korea. Specimens are occasionally recorded from exported timber throughout the world and it is thus thought to have become established in Brazil where pine trees are widely used for reforestation. In the UK it is thought to have declined over recent decades but remains locally common across Southern and Central England north to the Humber and is very local and rare further north and through Wales and the West Country. The species is generally associated with conifer woodland, including commercial plantations, but has occasionally been recorded from deciduous trees such as birch (Betula L.) in appropriate habitats, the usual hosts are pine (Pinus L.), spruce (Picea Mill.), larch (Larix Mill.) and fir (Abies Mill.) but other species are also likely be involved. Adults occur from April until July or August, they diurnal and active in warm weather when they visit a range of flowers to feed on pollen and nectar. Eggs are usually laid among damaged bark on recently damaged or cut branches and larvae initially develop under bark but as they grow they enter the xylem. Larval galleries are very distinctive, long, irregular, near-horizontal and often intersecting, they become deeper in late summer and larvae penetrate deeper to overwinter, development may continue over two or three years but pupation always occurs in the heartwood cell during July or August. Adults eclose during late summer but remain in the pupal cell until the following spring. Sweeping foliage or beating branches may produce adults but they are more readily found by searching flowers in warm weather, particularly umbels but they are sometimes appear on hawthorn and other blossom in numbers in the spring.
 Molorchus minor 1 |
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6.0-16.0 mm. Elongate and narrow with abbreviated elytra which leave the abdomen substantially exposed, forebody black to dark grey, elytra brown with an oblique yellow flash behind the middle, legs brown with the femora variously darker, antennae brown. Head transverse from above, with slightly converging temples and long narrow eyes that curve around the antennal tubercles, frons weakly depressed, vertex punctured, finely wrinkled longitudinally and with fine grey pubescence. Antennae filiform with the third segment much longer than the first; in females 11-segmented and reaching about the abdominal apex, in males 12-segmented and extending far beyond the abdominal apex. Pronotum elongate, angled laterally behind the middle and narrowed to distinct anterior angles and a sub-basal constriction, surface punctured and roughly sculptured, depressed across the middle and with a lustrous median tubercle either side and medially towards the base. Elytra slightly elongate with rounded shoulders and apical margins, each with an oblique pale keel in the posterior half, surface evenly and moderately strongly punctured, these may form longitudinal series on the disc and there may be longitudinal depression below the shoulders but without distinct striae. Legs long and slender, especially the tibiae, front femora dilated, middle and hind femora expanded only in the apical half. Tarsi pseudotetramerous and relatively short, claws simple and without a tooth at the base.
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Among our UK fauna this can only be confused with Glaphyra, here the third antennal segment is about as long as the first, the frons is deeply grooved and the elytra lack the oblique pale marking.