Dor beetle (Geotrupes stercorarius)
|Size||Length: 15 – 20 mm|
The dor beetle, for many people, is the archetypal ‘beetle’. It has the classic beetle shape and colouration, being oval in shape with a shiny domed body, with a blue sheen. The thorax is smooth but the wing cases are grooved longitudinally. The legs are also shiny black and strong with noticeable spikes. The head is small and the antennae short with fan-like tips. The dor beetle, more popularly known as the dung beetle, belongs to a sub-family called scarabs. These beetles were regarded as sacred by the ancient Egyptians.
The man whom has come to be most closely associated with the study of the dor beetle was the French entomologist Jean-Henri Fabre (1823 – 1915). Fabre was an amateur with no formal scientific training, but he was fascinated by insects and their behaviour. His books were readable and his enthusiastic style of writing made them very popular. He is regarded to this day as one of the most influential people in the study of insects.
The dor beetle is found throughout most of Europe, Asia and Africa. Similar species occur over most of the temperate and tropical countries.
Dor beetles are found wherever there are grazing herbivores. In temperate latitudes, they can be found in pastures and meadows, open woodland grazed by sheep or cattle, and they occasionally turn up in parks and gardens.
Anyone who has ever examined a cowpat will probably have noticed a patchwork of holes beneath it. These holes are made by the adult beetles burrowing down into the soil, taking with them particles of dung as food supplies for their larvae. Animal dung is rich in nutrient and dung beetles play an important role in returning much of this material to the soil. Their larvae, in eating much of this plant matter, make it more accessible to bacteria and other soil-living organisms which, in turn, allow the soil to maintain its fertility. In other parts of the world, relatives of the dor beetle make small balls of animal dung, which they roll away to suitable nest sites constructed underground.
Adults are strong fliers and can travel some distance in search of suitable food supplies for their young. Sometimes they turn up in parks and gardens and this is where people are most likely to find them on the ground. The adults are often infested with small copper-coloured mites, a phenomenon that has led to the beetles’ folk-name of ‘lousy watchman’.
The biggest threat to these beetles is the use of invermectin-based worming treatment for grazing animals. This chemical is used to treat intestinal worms in the animals’ gut but persists in their dung when it is deposited on the ground. The ivermectin effectively kills the developing larvae long after it has passed through the larger animal.
Although the dor beetle is not thought to be threatened as a species, they are linked to another animal which is the subject of several conservation projects. Dor beetles and their cousins, the chafers, are the main prey of greater horseshoe bats, a species that has been declining in numbers for many years. The cause of this is believed to be the use of the ivermectin-based wormers used in the intensive rearing of cattle. A reduction in the available insect food has affected greater horseshoe bat populations across the UK, and the bats are now limited to parts of the West Country and South Wales. Conservation projects to restore the fortunes of this mammal include limiting the use of ivermectin treatments and re-creating habitats suitable for the bats. As with so many endangered species, the solution to one problem frequently benefits other associated animals.
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- Larvae: stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.