Onthophagus fracticornis (Preyssler, 1790)
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POLYPHAGA Emery, 1886
SCARABAEOIDEA Latreille, 1802
ONTHOPHAGINI Burmeister, 1846
ONTHOPHAGUS Latreille, 1802
This is a widespread western Palaearctic species distributed from Portugal east to the Caspian Sea and from the Mediterranean borders north to the UK and Fennoscandia where it formerly extended into the northern provinces but following a recent and drastic decline is now restricted to southern and mostly coastal areas, it also extends through Asia Minor, Ukraine, Syria, and Iran and is present in western parts of North Africa. Through much of this range it is locally common but seems to have suffered a general and often severe decline in the north. In the UK it is a very local and rare species with only a few modern records from North Somerset, it was formerly known from Wales but has not been recorded there since the 1940s. The species occurs on a range of soil types and in various types of dung but mostly cattle, horse and sheep, here it generally occurs on well drained pasture, often on hillsides but has also been recorded from a marshland grazing area. Adults are present year-round; they are active from early spring until the autumn, peaking in April/May, when they breed and again in August/September when the new generation appears. The biology is typical of the group; they are quick to colonize fresh manure and after a period of feeding the female excavates a branched burrow beneath the dung, generally 20 to 30cm deep, while the male clears away excavated soil, and when the burrow is nearing completion he will form brood masses of dung and transport them down to the female who will pack then into chambers and lay a single egg into each. When burrows are excavated on very light and crumbly soil they may be lined with dung in order to stop them collapsing. Larvae develop through the spring and summer, passing through three instars before pupating within the remains of the brood mass during July and August. New generation adults are active from late summer until the autumn when they return to the soil to overwinter.
A distinctive bicoloured species with a dark and variously metallic forebody and mottled brown elytra, the lateral pronotal margins are sinuate behind the anterior angles and so the species is closely similar to two others on the UK list; from O. coenobita it may be distinguished by the black elytral epipleura (or at least the delimiting lateral carina is black) and less strongly metallic forebody, and from O. similis by the form of the head sculpture. The female has two ridges across the head, the posterior of which is broad, arcuate and slightly raised at the centre, in similis this ridge is narrower, straight and raised towards the edges; joining the lateral margins of these rigdes produces parallel lines in fracticornis whereas in similis they converge towards the base of the head. The cephalic horn in fracticornis is broad across the base and distinctly angled when viewed from in front, that of similis has a narrow base and is rounded rather than angled in front of the eyes. In side view the horn of fracticornis is strongly angled so that it points upwards at the tip whereas that of similis is smoothly curved and angled posteriorly. Diminutive male fracticornis can be very similar to male similis and here they will need to be dissected as the parameres are very different; in similis they are parallel and widely expanded apically while in fracticornis they are narrow to the apex and converge.