Hoverflies, sometimes called flower flies or syrphid flies, make up the insect family Syrphidae. As their common name suggests, they are often seen hovering or nectaring at flowers; the adults of many species feed mainly on nectar and pollen, while the larvae (maggots) eat a wide range of foods. In some species, the larvae are saprotrophs, eating decaying plant and animal matter in the soil or in ponds and streams. In other species, the larvae are insectivores and prey on aphids, thrips, and other plant-sucking insects. Aphids alone cause tens of millions of dollars of damage to crops worldwide every year; because of this, aphidophagous hoverflies are being recognized as important natural enemies of pests, and potential agents for use in biological control. Some adult syrphid flies are important pollinators. About 6,000 species in 200 genera have been described. Hoverflies are common throughout the world and can be found on all continents except Antarctica. Hoverflies are harmless to most other animals despite their mimicry of more dangerous wasps and bees, which serves to ward off predators.The size of hoverflies varies, depending on the species. Some, like members of the genus Baccha, are small, elongate and slender, while others, like members of Criorhina are large, hairy, and yellow and black. As members of Diptera, all hoverflies have a single functional pair of wings (the hindwings are reduced to balancing organs). They are brightly colored, with spots, stripes, and bands of yellow or brown covering their bodies. Due to this coloring, they are often mistaken for wasps or bees; they exhibit Batesian mimicry. Despite this, hoverflies are harmless. With a few exceptions (e.g.), hoverflies are distinguished from other flies by a spurious vein, located parallel to the fourth longitudinal wing vein. Adults feed mainly on nectar and pollen. They also hover around flowers, lending to their common name. Unlike adults, the maggots of hoverflies feed on a variety of foods; some are saprotrophs, eating decaying plant or animal matter, while others are insectivores, eating aphids, thrips, and other plant-sucking insects.This is beneficial to gardens, as aphids destroy crops, and hoverfly maggots are often used in biological control. Certain species, such as Lampetia equestris or Eumerus tuberculatus, are responsible for pollination. An example of a well-known hoverfly maggot is the rat-tailed maggot, of the drone fly, Eristalis tenax. It has a breathing siphon at its rear end, giving it its name. The species lives in stagnant water, such as sewage and lagoons. The maggots also have a commercial use, and are sometimes sold for ice fishing. On occasion, Hoverfly larvae have been known to cause accidental myiasis in humans. This occurs when the larva are accidentally ingested on food or from other sources. Myiasis causes discomfort, pain, or itching,however, Hoverflies do not normally prey upon humans and cases of myiasis from Hoverflies is very rare.Hoverflies are a cosmopolitan family found in most biomes, except deserts, tundra at extremely high latitudes, and Antarctica. Certain species are more common in certain areas than others; for example, the American hoverfly, Eupeodes americanus, is common in the Nearctic ecozone, and the common hoverfly, Melangyna viridiceps, is common in the Australasia ecozone. About 6,000 species and 200 genera are in the family. Larvae of hoverflies are often found in stagnant water. Adults are often found near plants, their principal food source being nectar and pollen. Some species are found in more unusual locations; for example, members of the genus Volucella can be found in bumblebee nests, while members of Microdon are myrmecophiles, found in ant or termite nests. Others can be found in decomposing vegetation. Hoverflies are important pollinators of flowering plants in a variety of ecosystems worldwide.[10] Syrphid flies are frequent flower visitors to a wide range of wild plants as well as agricultural crops and are often considered to be the second most important group of pollinators after wild bees. However, there has been relatively little research into fly pollinators compared with bee species.[10] It is thought that bees are able to carry a greater volume of pollen on their bodies, but flies may be able to compensate for this by making a greater number of flower visits. Like many pollinator groups, syrphid flies range from species that take a generalist approach to foraging by visiting a wide range of plant species to those which are specialists and are more selective in the plants they visit. Although hoverflies are often considered to be mainly non-selective pollinators some hoverflies species are highly selective and carry pollen from one plant species. It is thought that Cheilosia albitarsis will only visit Ranunculus repens. http://en.wikipedia.org/wiki/Hoverfly

• published: 02 Jun 2014
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