The term dung beetle refers to any of a number of species of beetle falling under the family Scarabaeoidea. As the name would imply, dung beetles are known for their affinity for dung. Many species of dung beetle survive exclusively on a diet of feces. Some dung beetles will roll excrement into little spheres that are used for food and as breeding chambers. Others bury dung inside the ground for safe-keeping, and still others simply live in animal manure.
Dung beetles are known for their agricultural benefits. Burying and consuming dung introduces beneficial microbes to the soil, aerates and mixes the soil, and spreads seeds that are deposited from animal feces. The soil benefits of dung beetles is so well known that several countries have explicitly introduced the insect for purpose of animal husbandry. Removing sources of animal feces also prevents the onset of pests such as flies and roaches, so dung beetles can actually be effective pest managers.
Dung beetles have long been in the cultural consciousness of humans. The dung beetle has come to signify transformation or coming into being. The ancient Egyptians considered several species of dung beetle sacred, most notably the sacred scarab (Scarabaeus sacer). Egyptian mythology likens the action of the dung beetle to that of Khepri, the god of the rising sun, as he rolls the sun over the sky every day.
Dung beetles, like all insects, have a body composed of 3 main segments: head, thorax, and abdomen. Their bodies are covered by a hard chitinous carapace that varies in color from black, brown, purple or yellow, depending on the species of dung beetle. A pair of wings lie folded under the elytra—hardened forewings that cover the top of the body. Each of their six legs is terminated with an appendage specialized for shoveling dung and earth. Some species have a pair of horns on their head, which they use for defense and to manipulate the environment. Dung beetles vary in size, with the smallest species averaging only 2mm long to the larger species that can measure almost 30 mm long.
Dung beetles are found on every continent except Antarctica, and live in most habitats; e.g. forests, savannas, deserts, urban areas, etc. The majority of species of dung beetle subsist on a diet of mostly feces. Many are exclusive feces eaters, though some species also eat decaying mushrooms, fruit, and vegetation. A handful of species, such as the Central American Deltochilum valgum, are carnivorous and eat small insects like millipedes. Most biologists divide dung beetles into three main types: tunnelers, rollers, and dwellers. Tunneler are known for taking dung and burying it while dwellers simply live in the manure.
Roller dung beetles are known for collecting and rolling dung into balls, which they store for food and breeding purposes. Dung beetles will search for feces using their sense of smell. Once finding dung, they will roll it up into a ball, and keep rolling in a straight line regardless of obstacles. Sometimes, dung beetles will even attempt to steal balls from other beetles, leading to confrontation. Dung beetles are strong and can roll balls up to 10 times their weight with relative ease; a rather Herculean feat of strength. The taurus scarab beetle (Onthophagus taurus) has been observed to pull up to 1,141 times their own body weight, the equivalent of an average human pulling 6 double-decker buses full of people. The Indian scarab is known to make balls of dung covered in clay which become so hard when dried, they were once thought to be old stone cannonballs.
Once rolling a ball of suitable size, the beetle will take it back to its den. Both males and females work together to dig a nest and burrow under a dung source, where the freshly rolled dung ball is stored. Once a male and female mate, the female will then lay her eggs in the ball, so that the hatched larva have an immediate food source. This peculiar behavior led the ancient Romans to believe that there were no female dung beetles—they believed the larvae spontaneously generated from the dung after being endowed by the male’s vital essence.
Dung beetles are particularly good navigators. They are the only known species that navigates using polarized light reflected from the moon, and there is also evidence that they can navigate using the light from stars and the Milky Way galaxy.
Dung beetles play an important role in modern agricultural practices. The activity of dung beetles burying and consuming dung aerates soil and recycles nutrients necessary for healthy plant growth. Removing sources of feces also prevents the onset of pests like flies and roaches which can be bad for crops and livestock. In tropical areas, they consume and disperse seeds found in animal dung, which influences seed burial and the spread of tropical plants.
Several countries have imported species of dung beetles to aid in agricultural efforts. In Australia between the 1960s-1980s the Commonwealth Scientific and IndustrialResearch Organization (CSIRO) saw the introduction of 23 novel species of dung beetle from South Africa and Europe, which greatly improved agricultural quality and reduced populations of bush fly pests by almost 90%. Currently, the nation of New Zealand is considering a similar proposal, which will result in the introduction of 11 new species of dung beetle to agricultural areas in New Zealand.
Dung beetles have also been introduced into various regions in North and South America, where they have been shown useful for eliminating sanitary issues related to animal dung and for controlling disease in cattle populations. It is estimated that the activity of dung beetles saves the US cattle industry 380 million dollars a year by burying livestock feces.
In addition to being beneficial for agriculture, many countries use the dung beetle as an agricultural product itself. Dried dung beetle is a popular ingredient in traditional Chinese medicine, said to help treat seizures, and in Thailand, dung beetles are a common food item along with other insects.
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