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| Dung beetle | |
|---|---|
 | |
| Scarabaeus viettei (syn.Madateuchus viettei,Scarabaeidae) indry spiny forest close toMangily, westernMadagascar | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Coleoptera |
| Suborder: | Polyphaga |
| Infraorder: | Scarabaeiformia |
| Superfamily: | Scarabaeoidea |
| Groups included | |
| Cladistically included but traditionally excluded taxa | |
Dung beetles arebeetles thatfeed on feces. Allspecies of dung beetle belong to the superfamilyScarabaeoidea, most of them to the subfamiliesScarabaeinae andAphodiinae of the familyScarabaeidae (scarab beetles). As most species of Scarabaeinae feed exclusively on feces, that subfamily is often dubbedtrue dung beetles. There are dung-feeding beetles which belong to other families, such as theGeotrupidae (theearth-boring dung beetle). The Scarabaeinae alone comprises more than 5,000 species.[1]
As they do not belong to a single group sharing acommon ancestor, there is a diversity in the behavior of dung beetles, including the iconic dung-rolling behavior revered byAncient Egyptians asKhepri rolling thesun across the sky.
Dung beetles are not a single taxonomic group (they are notmonophyletic); dung feeding is found in a number of families of beetles, so the behaviour cannot be assumed to have evolved only once. Below is the taxonomy of beetles, with a delineation of which taxa are considered dung beetles:
Dung beetles live in manyhabitats, including desert,grasslands andsavannas,[5]farmlands, and native and plantedforests.[6] They are highly influenced by the environmental context,[7] and do not prefer extremely cold or dry weather. They are found on all continents exceptAntarctica. They eat the dung ofherbivores andomnivores, and prefer that produced by the latter.[8] Many of them also feed onmushrooms anddecayingleaves andfruits. TheNeotropicalDeltochilum valgum,D. kolbei andD. viridescens are carnivores with a strong preference for preying uponmillipedes.[9] Two other species from Brazil,Canthon dives andCanthon virens, prey on queens and other winged forms ofleafcutter ants.[10] One species from theIberian Peninsula,Thorectes lusitanicus, feeds on acorns.[11] Dung beetles do not necessarily have to eat or drink anything else, because the dung provides all the necessarynutrients.[citation needed][relevant?] There are dung beetle species of various colors and sizes, and some functional traits such as body mass and leg length can have high levels of variability.[7]
The behavior of the beetles was poorly understood until the studies ofJean Henri Fabre in the late 19th century. For example, Fabre corrected the myth that a dung beetle would seek aid from other dung beetles when confronted by obstacles. By observation and experiment, he found the seeming helpers were in fact awaiting an opportunity to steal the roller's food source.[12]
Cambefort and Hanski (1991) classified dung beetles into three functional types based on their feeding and nesting strategies:Rollers,Tunnelers, andDwellers. The "rollers" roll and bury a dung ball either for food storage or for making a brooding ball. When brooding, two beetles, one male and one female, stay around the dung ball during the rolling process. Usually it is the male that rolls the ball, while the female hitch-hikes or simply follows behind. In some cases, the male and the female roll together. When a spot with soft soil is found, they stop and bury the ball, thenmate underground. After the mating, one or both of them prepares the brooding ball. When the ball is finished, the female lays eggs inside it, a form ofmass provisioning. Some species remain to guard their offspring after laying. The dung beetle goes through a completemetamorphosis. The larvae live in brood balls made with dung prepared by their parents. During the larval stage, the beetle feeds on the dung surrounding it.[citation needed]
Tunnelers, such asEuoniticellus intermedius, bury the dung wherever they find it. A third group, thedwellers, neither roll nor burrow: they simply live within dung.[citation needed]
Most dung beetles search for dung using their sensitivesense of smell. Some smaller species simply attach themselves to the dung-producing animals to wait for dung. After capturing the dung, a dung beetle rolls it, following a straight line despite all obstacles. Sometimes, dung beetles try to steal the dung ball from another beetle, so the dung beetles have to move rapidly away from a dung pile once they have rolled their ball to prevent it from being stolen. The strength of dung beetles is well-known; maleOnthophagus taurus can pull 1,141 times their own body weight, the equivalent of an average person pulling sixdouble-decker buses full of people.[13] The daily dung of oneelephant can support 2,000,000 beetles.[14] Some species of dung beetles can bury dung 250 times their own mass in one night.[15] They are often attracted by the feces collected byburrowing owls.[citation needed]
Thenocturnal African dung beetleScarabaeus satyrus is one of the few known invertebrate animals that navigate and orient themselves using theMilky Way.[16][17] The AfricanScarabaeus zambesianusnavigates bypolarization patterns inmoonlight,[18] the first animal known to do so.[19][20][21][22] Dung beetles can also navigate when only theMilky Way or clusters of bright stars are visible,[23] making them the only insects known to orient themselves by the Milky Way.[24][23] Research using 1 kg bolus of elephant dung found that a larger number exploit it during the night (13,700) than during the day (3,330).[14] The eyes of dung beetles are superpositioncompound eyes typical of many scarabaeid beetles;[25][26]
The following sequence of images shows a beetle rolling a dung ball, orienting itself prior to going:
_1_of_4.jpg)
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_4_of_4.jpg)
They are widely used in ecological research as a goodbioindicator group to examine the impacts of climate disturbances, such as extreme droughts[27] and associated fires,[28] and human activities on tropical biodiversity[29][30] and ecosystem functioning,[31] such as seed dispersal, soil bioturbation andnutrient cycling.[28]
Dung beetles play a role inagriculture andtropical forests. By burying and consuming dung, they improve nutrient recycling and soil structure.[32][33] Dung beetles have been further shown to improve soil conditions and plant growth on rehabilitated coal mines in South Africa.[34] They are also important for the dispersal of seeds present in animals' dung,[35] influencing seed burial and seedling recruitment in tropical forests.[36] They can protect livestock, such ascattle, by removing the dung which, if left, could provide habitat forpests such asflies. Therefore, many countries haveintroduced the creatures for the benefit ofanimal husbandry. TheAmerican Institute of Biological Sciences reports that dung beetles save theUnited States cattle industry an estimatedUS$380 million annually through burying above-ground livestock feces.[37]
In Australia, theCommonwealth Scientific and Industrial Research Organisation (CSIRO) commissioned theAustralian Dung Beetle Project (1965–1985) which, led byGeorge Bornemissza, sought to introduce species of dung beetles from South Africa and Europe. The successful introduction of 23 species was made, most notablyDigitonthophagus gazella andEuoniticellus intermedius, which has resulted in improvement of the quality and fertility of Australian cattle pastures, along with a reduction in the population of pestilentAustralian bush flies by around 90%.[38][39] In 1995 it was reported that dung beetles were being trialled in the Sydney beach suburb ofCurl Curl to deal with dog droppings.[40]
An application made byLandcare Research to import up to 11 species of dung beetle intoNew Zealand[41] was approved in 2011.[42] As well as improving pasture soils the Dung Beetle Release Strategy Group said that it would result in a reduction in emissions ofnitrous oxide (agreenhouse gas) from agriculture.[43] There was, however, strong opposition from some at theUniversity of Auckland, and a few others, based on the risks of the dung beetles acting as vectors of disease.[44][45] There were public health researchers at the University of Auckland who agreed with theEnvironmental Protection Authority's risk assessment.[46] Several Landcare programmes in Australia involved schoolchildren collecting dung beetles.[47]
The African dung beetle (D. gazella) was introduced in several locations in North andSouth America and has been spreading its distribution to other regions by natural dispersal and accidental transportation, and is now probably naturalized in most countries betweenMexico andArgentina. The exotic species might be useful for controlling diseases oflivestock in commercial areas, and might displace native species in modified landscapes; however, data is not conclusive about its effect on native species in natural environments and further monitoring is required.[48]
The Mediterranean dung beetle (Bubas bison) has been used in conjunction withbiochar stock fodder to reduce emissions ofnitrous oxide andcarbon dioxide, which are both greenhouse gases. The beetles work the biochar-enriched dung into the soil without the use of machines.[49]
Scientists inCanberra in 1965 discovered that Dung beetles (Scarabaeids), specificallyOnthophagus australis Guérin-Méneville, improve plant yields using their dung.Japanese millet was studied and data on nutrient uptake. These plants were placed in pots lackingnitrogen,phosphorus, andsulfur.Cow-dung was then added in treatment groups with or withoutO. australis. Some treatment groups even had two out of the three nutrients supplemented in the pots. Comparisons of the treatment and control groups were made to show that top growth and roots significantly increased when the dung was mixed well into the soil in the pots. Results showed that dung beetle activity greatly improved plant life. The dung has little impact alone, but in combination with the dung beetle, the nutritional value for the plants increases greatly. This suggests that dung beetles have many positive implications for the environment, including a beneficial role with plant life.[50]
Some dung beetles areused as food inSouth East Asia and a variety of dung beetle species have been usedtherapeutically (and are still being used in traditionally living societies) in potions andfolk medicines to treat a number of illnesses and disorders.[51]
InIsan, Northeastern Thailand, the local people eat many different kinds of insects, including the dung beetle. There is an Isan song: "กุดจี่หายไปใหน" or "Where Did the Dung Beetle Go?", which relates the replacement ofwater buffalo with the"metal" buffalo, which does not provide the dung needed for the dung beetle and has led to the increasing rarity of the dung beetle in the agricultural region.[citation needed]
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| ḫpr inhieroglyphs | ||
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Several species of the dung beetle, most notably the speciesScarabaeus sacer (often referred to asthe sacred scarab), enjoyed a sacred status among theancient Egyptians. Egyptian hieroglyphic script uses the image of the beetle to represent atriliteral phonetic that Egyptologists transliterate asxpr orḫpr and translate as "to come into being", "to become" or "to transform". The derivative termxprw orḫpr(w) is variously translated as "form", "transformation", "happening", "mode of being" or "what has come into being", depending on the context. It may have existential, fictional, or ontologic significance.
The scarab was linked toKhepri ("he who has come into being"), the god of the risingsun. The ancients believed that the dung beetle was only male-sexed, and reproduced by depositingsemen into a dung ball. The supposed self-creation of the beetle resembles that of Khepri, who creates himself out of nothing. Moreover, the dung ball rolled by a dung beetle resembles the sun.Plutarch wrote:
The race of beetles has no female, but all the males eject their sperm into a round pellet of material which they roll up by pushing it from the opposite side, just as the sun seems to turn the heavens in the direction opposite to its own course, which is from west to east.[52]
The ancient Egyptians believed that Khepri renewed the sun every day before rolling it above the horizon, then carried it through the other world after sunset, only to renew it, again, the next day. SomeNew Kingdom royal tombs exhibit a threefold image of the sun god, with the beetle as symbol of the morning sun. The astronomical ceiling in the tomb ofRamses VI portrays the nightly "death" and "rebirth" of the sun as being swallowed byNut, goddess of the sky, and re-emerging from her womb as Khepri.
Excavations of ancient Egyptian sites have yielded images of the scarab inbone,ivory, stone,Egyptian faience, and precious metals, dating from the Sixth Dynasty and up to the period of Roman rule. They are generally small, bored to allow stringing on a necklace, and the base bears a brief inscription orcartouche. Some have been used asseals.Pharaohs sometimes commissioned the manufacture of larger images with lengthy inscriptions, such as thecommemorative scarab of QueenTiye. Massive sculptures of scarabs can be seen atLuxor Temple, at the Serapeum in Alexandria (seeSerapis) and elsewhere in Egypt. The image of the scarab, conveying ideas of transformation, renewal, and resurrection, is ubiquitous in ancient Egyptian religious andfunerary art.
The scarab was of prime significance in the funerary cult of ancient Egypt. Scarabs, generally, though not always, were cut from green stone, and placed on the chest of the deceased. Perhaps the most famous example of such "heart scarabs" is the yellow-greenpectoral scarab found among the entombed provisions ofTutankhamen. It was carved from a large piece ofLibyan desert glass. The purpose of the "heart scarab" was to ensure that the heart would not bear witness against the deceased at judgement in the Afterlife. Other possibilities are suggested by the "transformation spells" of theCoffin Texts, which affirm that the soul of the deceased may transform (xpr) into a human being, a god, or a bird and reappear in the world of the living.
One scholar comments on other traits of the scarab connected with the theme of death and rebirth:
It may not have gone unnoticed that the pupa, whose wings and legs are encased at this stage of development, is very mummy-like. It has even been pointed out that the egg-bearing ball of dung is created in an underground chamber which is reached by a vertical shaft and horizontal passage curiously reminiscent of Old Kingdom mastaba tombs."[53]
In contrast to funerary contexts, some of ancient Egypt's neighbors adopted the scarab motif forseals of varying types. The best-known of these being JudeanLMLK seals (8 of 21 designs contained scarab beetles), which were used exclusively to stamp impressions on storage jars during the reign ofHezekiah.
The scarab remains an item of popular interest thanks to modern fascination with the art and beliefs of ancient Egypt. Scarab beads in semiprecious stones or glazed ceramics can be purchased at most bead shops, while at Luxor Temple a massive ancient scarab has been roped off to discourage visitors from rubbing the base of the statue "for luck".
InAesop's fable "The Eagle and the Beetle", the eagle kills a hare that has asked for sanctuary with a beetle. The beetle then takes revenge by twice destroying the eagle's eggs. The eagle, in despair, flies up toOlympus and places her latest eggs inZeus's lap, beseeching the god to protect them. When the beetle finds out what the eagle has done, it stuffs itself with dung, goes straight up to Zeus and flies right into his face. Zeus is startled at the sight of the unpleasant creature, jumping to his feet so that the eggs are broken. Learning of the origin of their feud, Zeus attempts to mediate and, when his efforts to mediate fail, he changes the breeding season of the eagle to a time when the beetles are not above ground.
Aristophanes alluded to Aesop's fable several times in his plays. InPeace, the hero rides up to Olympus to free the goddess Peace from her prison. His steed is an enormous dung beetle which has been fed so much dung that it has grown to monstrous size.
Hans Christian Andersen's "The Dung Beetle" tells the story of a dung beetle who lives in the stable of the king's horses in an imaginary kingdom. When he demands golden shoes like those the king's horse wears and is refused, he flies away and has a series of adventures, which are often precipitated by hisfeeling of superiority to other animals. He finally returns to the stable having decided (against all logic) that it is for him that the king's horse wears golden shoes.[54]
InFranz Kafka'sThe Metamorphosis, the transformed character of Gregor Samsa is called an "old dung beetle" (alter Mistkäfer) by acharwoman.
I ask myself in vain what Proudhon introduced into Scarabaean morality the daring paradox that 'property means plunder', or what diplomatist taught the Dung-beetle the savage maxim that 'might is right'.
{{cite web}}: CS1 maint: numeric names: authors list (link){{cite journal}}: CS1 maint: numeric names: authors list (link)Mr Pow said his innovative farming system could help livestock producers become more profitable while helping to address the impact of climate change.
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