Geotrupes mutator (Marsham, 1802)

This very widespread though mostly very local and rare species occurs throughout Europe from Portugal east to Asia Minor and the Caucasus and north to the UK and the southern provinces of Fennoscandia, otherwise it is among the most widespread of the Palaearctic species, extending through the south of Siberia to the far east of China. It is the rarest of our U.K. Geotrupes and seems to have declined in recent decades; there are a few widely scattered records through England north to the Wash with most from the southeast and around the Severn estuary, further north there are very few, mostly coastal, records extending to the Scottish border. The species is mainly associated with horse and cattle dung on open pasture, adults occur year round; they are active from March until October with peaks in the spring and autumn. Mating occurs in the spring and adults dig vertical galleries directly beneath dung pats, the female then excavates brood chambers at intervals along the main gallery which she provisions with dung and lays a single egg before sealing them with soil from the next brood chamber. Larval development is relatively rapid and they are fully-grown within two or three months, they pupate within the brood chamber and new generation adults appear from the middle of August until October. Adults are crepuscular and nocturnal and may be found flying over pasture during the evening, they are attracted to light and usually infested with phoretic mites. The thermoregulatory behaviour of this species has been studied on a cattle farm in Spain and it seems the beetles are able to increase their body temperature in response to decreasing light intensity, allowing them to be active during autumn and winter evenings. For more information click HERE.

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This is a large and very distinctive species; 15-26mm, broadly elongate and very convex, the dorsal surface varies from black to violet, blue or golden metallic but UK specimens are generally distinctly metallic green, the underside is metallic green or blue-green, and the abdomen is more densely punctured and pubescent towards the lateral margins. The pronotum is smoothly convex with a complete basal border and sparse fine punctures across the disc which become larger and denser towards the lateral margins, and a median longitudinal impression or row of coarse punctures in the basal half. Elytra with nine well-impressed and complete striae between the suture and the humeral callus. Hind tibiae with three complete transverse carina, including the terminal one.