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Pterostichus macer (Marsham, 1802)

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ADEPHAGA Clairville, 1806

CARABIDAE Latreille, 1802

PTEROSTICHINAE Bonelli, 1810

PTEROSTICHINI Bonelli, 1810

Pterostichus Bonelli, 1810

Adelosia Stephens, 1835

Locally common across southern Europe from Spain to Greece but becoming less so and generally rare further north where it reaches the UK, Denmark and Latvia, in many northern regions it is red-listed and known from only a few records. The eastern extent of the distribution is unclear but it occurs extensively through Asia Minor and there are isolated records as far as Western Siberia. In the UK it is locally common across England as far north as Cumbria although there are very few records from the West Country and Wales and these tend to be coastal. This mostly terrestrial species occurs in a wide range of habitats from open grassland to moorland, parkland, gardens and salt marshes, usually on heavy and slow-draining soils with dense but patchy vegetation, adults spend much of their time in the soil and, while they are not halophilic, may frequently be found in cracks and crevices as coastal flats dry in the summer. Adults are present year-round; they are active from March until September and rarely found earlier or later, no doubt due to their secluded lifestyle, and peak in abundance during April and May. The species is active on the surface at night but otherwise remains in the soil or under stones or debris, adults are predatory and from studies of gut-content they feed mostly on aphids and avoid spiders. Adults may be found by pit-falling or nocturnal searching on soils that remain damp through the summer, they are sometimes common in flood refuse, occasionally occur under bark and, at least on the continent, are sometimes attracted to light traps. So far as is known the adults are macropterous.

10.5-14.0 mm. Elongate, flattened and discontinuous in outline, shiny dark brown to black with dark antennae and reddish legs. Head convex and prominent eyes and near-parallel cheeks and temples, dorsal surface flat and without structure but for two depressions behind the fronto-clypeal suture, each side with two supra-orbital punctures. Mandibles notably broad and robust to narrow and curved tips. Antennae densely pubescent from the fourth segment. Pronotum weakly transverse, broadest and smoothly curved in front of the middle and strongly narrowed and sinuate to sharp and protruding posterior angles, surface mostly impunctate, narrowly impressed along the centre and with weakly impressed basal fovea; the inner long and straight and the outer shorter and often almost obliterated. Elytra parallel-sided or only weakly dilated from rounded shoulders to a continuous apical margin, with well-impressed and impunctate striae, including a scutellary striole, and weakly convex or almost flat interstices; the third with three punctures, the third of which is fine and situated close to the apical margin. Front tibiae with a strong antenna-cleaning notch, tarsi not furrowed dorsally. Basal segments of pro-tarsi dilated in males. This species is easily recognized in the field by its large size and much flattened form.

Pterostichus macer

Pterostichus macer

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