Onthophagus nuchicornis (Linnaeus, 1758)
This is a very widespread Palaearctic species; it is generally common across Europe from the Mediterranean north to the northern provinces of Fennoscandia and extending east from Portugal through Asia Minor and Russia to China, it is also widespread across northern North America and Canada following accidental introductions during the nineteenth century, and in 1910 it was imported to Hawaii to help control the horn fly, a livestock pest, but failed to become established. Here it is a very local and rare species with recent coastal records from Wales, Devon, East Sussex, Kent and Hampshire, and also a very few inland records from Hampshire and East Anglia, it is thought to be in general decline, as it is in other northern European areas, but the historical distribution is very difficult to assess because of possible confusion with a closely similar species, O. similis (Scriba, 1790), which is generally common and overlaps in distribution. Adults are active from April until September, peaking in the spring and autumn, on the continent they display a preference for cattle dung but here they have been found in horse, cattle, sheep, rabbit and canine droppings. The typical habitat is coastal dunes or exposed grassland or other open areas on loose sandy soils, the life cycle is typical of the genus with both adults and larvae feeding on dung; mating occurs in the spring and adults burrow beneath or near to the host material, the burrows are branched to produce brood-chambers which are provisioned with dung into which a single egg is laid, larvae develop through the spring and summer and pupate in late summer to produce adults that will overwinter. On the continent the adults have been observed feeding on decaying plant material and fungal fruiting bodies and have been found on carrion.
Adults may be recognized by the combination of black pronotum, bicoloured elytra, and smoothly rounded pronotal margin. 6-9mm. Head and pronotum black, without a metallic reflection, and finely punctured and pubescent; female head with two transverse ridges, male head with a long backwardly-produced horn. Pronotum transverse and more or less evenly rounded behind protruding anterior angles; the margin may be almost straight towards the angles but it is never sinuate, as in O. similis, anterior margin produced medially, more strongly so in the female. Elytra transverse and evenly rounded, with shallow unpunctured striae and weakly convex and finely punctured interstices; colouration varies widely and both very pale and very dark specimens are found on the continent but typically with a rather random series of well-defined dark markings on a pale to dark yellowish-brown ground colour, in this species the dark colour extends to the base of the fifth interstice.