We muck out our horse paddock twice a day. In the late summer and autumn, there are usually one to three dark-blue iridescent beetles sitting in burrows beneath the horse droppings. How do they get there in such a short time, which is perhaps 12 hours at most? Do the beetles come through the soil (which is often very hard and dry in the summer) or do they travel over the ground?
鈥� The beetles burrowing in the horse droppings have almost certainly flown there, attracted by the smell. They are likely to be dung beetles, of the family Scarabaeidae (scarab beetles). Dung beetles are loosely divided into rollers, burrowers and dwellers. Rollers will roll a ball of dung away and bury it for food or egg-laying. Burrowers dig down into the dung, feeding and breeding inside it. Dwellers live on top of the dung. Your beetles seem to be burrowers.
Most dung beetles have an exquisitely sensitive sense of smell and are powerful flyers. To avoid competition, and lessen the risk of the dung drying out and becoming impossible to mine, the beetles arrive very quickly.
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I worked for 20 years in Zambia and frequently had to take trips into the bush. On one occasion I was driving alone on a remote road and pulled over to relieve myself. As I crouched, there was a loud buzzing and, when I stood up, I saw a dung beetle had arrived and was already hard at work, expertly forming a portion into a ball. Having done so, the beetle hurried away with it.
As I watched, grimly fascinated, another arrived on the wing, and then another, and another. I was so astonished that I didn鈥檛 think to count how many there were, but within 30 minutes there wasn鈥檛 a trace of my faeces left. Still more dung beetles flew in, presumably attracted by the residual smell, and wandered around forlornly. It was one of my more memorable wildlife experiences.
Alistair Scott, Gland, Switzerland
鈥� Some years ago I released five species of dung beetle on to our farm in southern New South Wales. These species originated in South Africa, and after years of testing were allowed into Australia, along with other species.
The reason that the beetles arrive on the dung so quickly is that they are strong flyers, some with quite a loud buzz.
Eggs are laid in cowpats, and the larvae hatch in about three days and dig tunnels, pulling the dung down. This kills any fly larvae that are present, which take five days to hatch.
鈥淒ung beetle eggs are laid in cowpats, and the larvae hatch in about three days and dig tunnels鈥�
A fly can lay about 3,000 eggs on one cowpat, so the improvement of my farm pasture and the reduction of fly numbers have been striking.
David Hamilton, Sydney, Australia
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This article appeared in print under the headline 鈥淒ung addicts鈥�