Chaetocnema picipes Stephens, 1831
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POLYPHAGA Emery, 1886
CHRYSOMELOIDEA Latreille, 1802
Tlanoma Motschulsky, 1845
Widespread and locally common throughout most of the Palaearctic region, from Europe and North Africa east through Russia and Asia Minor to eastern Siberia, China and Korea, also recorded from tropical Africa and Madagascar. In Europe it is known from the Pyrenees to Italy and Bulgaria and north to the UK, Denmark and the Baltic countries, extending into southern Sweden and Norway. In the UK it was formerly confused with C. concinna and so the distribution remains tentative but it is locally common across south east and Central England and there are scattered records from the West Country, Wales, further north to Yorkshire and in Ireland. The species is not a recent arrival as there are specimens dating back to the mid-1800s in collections. Adults are present year-round; they overwinter among tussocks and litter and are active from March until October, peaking in abundance during June and again in late summer/autumn. Typical habitats are grassland, heathland and woodland borders and they often occur in disturbed areas such as road verges, parks and gardens. Larvae develop low down in stems or in roots during spring and summer but host plants are uncertain. Adults are associated with a range of Polygonaceae including Knotgrass (Polygonum aviculare L.) as well as wild and cultivated plants from other families e.g. species of Chenopodium L., Atriplex L , Beta L. and Amaranthus L. (Amaramthaceae), and the species is an occasional pest of Oilseed Rape (Brassica napus L. (Brassicaceae). Adults will be found by general sweeping or in flight-interception traps.
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1.7-2.3mm. Elongate-oval and discontinuous in outline, glabrous, body entirely dark metallic bronze, coppery or greenish, antennae dark with several basal segments paler, at least ventrally, legs extensively dark but usually with the tibiae and tarsi to some extent brown. Head with large convex eyes and a distinct vertical ridge between the antennal insertions, frontal furrows distinct
and curved downwards medially, usually touching the upper margin of the vertical ridge surface with punctures confined about the upper margins of the eyes. Antennae 11-segmented and simply filiform, terminal segment narrow, more-or-less symmetrical and pointed apically. Pronotum transverse; broadest across the base and narrowed to distinct frontal tubercles, apical and basal margins evenly curved, surface moderately-strongly punctured and with small and often indistinct basal furrows, without a transverse impression across the base. Elytra broadest in front of the middle and evenly curved from sloping shoulders to a continuous apical margin. Elytral striae punctured and distinct to the apex; the inner striae are sometimes wavy on the disc but always distinct and not confused with those of adjacent striae, interstices slightly convex and very finely punctured. Hind femora massively developed, front and middle tibiae normal. Middle and hind tibiae with a distinct external tooth towards the apices, hind tibiae with a single apical spur. Males may be distinguished by the dilated basal pro-tarsomere.
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Very similar to C. concinna, with which it sometimes found, but distinguished by the more slender, symmetrical and pointed last antennal segment; in concinna this is wider, asymmetric (needs to be viewed from several angles) and rounded or only obscurely angled.