Diachromus germanus (Linnaeus, 1758)

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ADEPHAGA Clairville, 1806

CARABIDAE Latreille, 1802

HARPALINAE Bonelli, 1810

ANISODACTYLINI Lacordaire, 1854

Diachromus Erichson, 1837

This widespread Palaearctic species extends from Europe through the Caucasus, Asia Minor, Iran and Syria to northwest China and is known from northwest Africa, in Europe it is locally common the south from Portugal to Greece and on many of the Mediterranean islands but becomes progressively less so further north; it extends to Denmark and Latvia but is otherwise absent from the Baltic region, here, and across the north generally, there has been a gradual decline since 1900 and the species is now either very rare or no longer present at many of its former sites. In the UK it very occasionally occurs along the southern and eastern coasts of England; it was first recorded in 1816 and this was followed by a few more records which lead to the belief that it was native but this is not supported by the fossil record or by any stable colonies and it is most likely that any UK records are from continental immigrants. There were very few records from the 20th century, the last being in 1906, and the species was for a while considered to be extinct here but a few very recent records from the south coast would suggest the species occasionally arrives from the continent rather than maintains breeding populations. Typical habitats in the UK are open grassland and arable land on dry or calcareous soils exposed to the sun, this is more or less the same in Northern Europe but here it also occurs on woodland borders and in clearings and hedgerows, in Central Europe it is more typical of woodland, arable land and undisturbed wasteland and in Southern Europe it is restricted to permanently damp grassland and open wetland situations, always exposed to the sun. Adults are diurnal although they spend most of their time under stones etc., and become active only in warm sunshine, they fly well and disperse locally but only warm weather and they usually occur singly. On the continent the abundance varies greatly from year to year and there are occasional years where they are locally common in the north, perhaps corresponding to UK arrivals, but more generally they occur in small numbers. Adults overwinter in sheltered situations under stones or in the soil and are active over a long season from March or April, they breed in the spring and new generation adults appear from late summer. The biology is largely unknown and larvae have not been described but adults are known to be at least partially phytophagous, they climb grass stems to obtain seeds and pollen which they then consume in situ or bury in subterranean storage cells, perhaps as provisions for their larvae or to consume during the winter, among those which seem to be favoured are Rough-stalked meadow-grass (Poa trivialis L.) and Meadow soft grass (Holcus lantanus L.)  Adults are usually found by searching under debris or among grass, they may be swept from grass seed heads on warm days and on the continent they occasionally appear in swarms flying low over grassland, alighting on seed heads to feed and taking flight after a few minutes.

Diachromus germanus 1

Diachromus germanus 1

7.5-10.0 mm. Easily distinguished among our UK fauna by the colour and general appearance. Head, elytra and appendages reddish-brown, pronotum, scutellum and a large apical spot on the elytra metallic blue or greenish-blue. Entire upper surface finely punctured and pubescent. Frons with a single setiferous puncture beside each eye. Antennae densely pubescent from the third segment. Pronotum transverse, broadest just in front of the middle and strongly sinuate before sharp posterior angles, surface densely punctured, confluently so in places, with long and deep basal fovea and a single setiferous puncture inside the posterior angles. Elytra almost parallel-sided from rounded shoulders to a distinct subapical constriction, striae well impressed to the apex and interstices flat and without fovea or setiferous punctures. Basal front tarsal segments dilated in males.