There are over 600 species world wide (mostly tropical), but only eight species from this family in the U. K. and the adults range in size from 7 - 26 mm. Some books place this family of beetles in the Scarabidae, They are the earth boring dung beetles who lay their eggs in dung or decaying vegetation. In some species these burrows can extend for two metres. In the U. K. beetles from this family are to be found anywhere there are large mammals.
Geotrupes stercorarius, Dor beetle, above and below, this individual was found on the pavement next to some woodland early on a May morning. It is also known as the Lousy watchman as it is often infested with mites. The word "dor" comes from an old word meaning drone. It is fairly common in the U. K. It differs from Geotrupes stercorosus, below, in having a fairly large depression on either side of its thorax, clearly seen in the photograph above. The underside is often hairy with the most beautiful metallic blue, green, violet or coppery sheen. Adult body length ranges from 16 - 26 mm.
This species can produce a chirping sound by rubbing its hind legs together. They swarm on still evenings producing a deep hum as they fly. They will fly towards light. On locating dung they burrow beneath it, and carry some dung to a chamber they widen out at the end of the tunnel, then the female lays her eggs. They favour cow or horse dung, and both male and female work together in digging tunnels and chambers. Both adults and larvae feed on dung. Adults can be seen quite late in the year, weather permitting, and will overwinter the coldest months in their burrows.
Although, to us humans, they lead ar rather unsavoury life, rarely have I come across anything more beautiful, the deep sheen reminds me of that found on the best old Japanese lacquerer.
Though beetles in the Geotrupes genus are large and heavy-looking they can and do fly both during the night and day.
The adults emerge from the soil on warm nights and take flight in search of dung. The beetle above was found lying dead on some steps in Rhodes. It is probably Geotrupes stercorosus, now renamed Anoplotrupes stercorosus, a dung beetle commonly found on the island, and all over Europe, on hillsides, woodland and moorland. Adults are 14 - 20 mm long, black or blue/black with a metallic blue or green sheen.
The adults mate in spring then the male and female dig a tunnel below the dung (they prefer the dung of herbivorous mammals, and work fast enough to bury almost a whole cow pat in a single night).
The tunnel is around 40 - 60 cm deep and branches at the end into 4 - 6 chambers. In each chamber an egg is laid. Then the adults drag dung down and fill the chamber with it.
The parents supply the growing larva with fresh dung. The larvae usually take just over a year to develop, so the lifecycle takes 2 years. Geotrupes adults also dig shallower tunnels to store dung for their own consumption. They will also eat rotting fungi. Geotrupes larvae can stridulate, producing a high-pitched noise by rubbing a row of teeth on the hind leg, against a series of ridges on the second leg. The noise may deter predators or parasites.