Thick-legged Hover Fly

Syritta pipiens is a species of hoverfly within the family Syrphidae. They are commonly found on flowers and have distinctive features such as broad femora, small white spots on the thorax, and large eyes. They belong to the subfamily Eristalinae and are closely related to the dronefly, Eristalis tenax. Syritta pipiens is cosmopolitan, found in North America, Asia, and Europe, and is often found in farmland, gardens, and parks. Their larvae feed on decaying organic matter, while adult flies feed on various flower species. They are important bio-control agents of plant pests and serve as pollinators, but are also sensitive to landscape changes and climate change.

Morphology

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The species Syritta pipiens is within the family of Syrphidae, commonly called hover or flower flies. Syrphidae is one of the largest families within the Diptera order and contains about 6,000 known species widely distributed around the world. They are distinctive flies that are often found on flowers, where the adult males primarily feed on nectar and adult females eat protein-rich pollen to produce eggs.The name “thick-legged hoverfly” comes from the fly’s distinctively broad femora. A thick-legged hoverfly has a wing length ranging between 4.25–7 mm (0.167–0.276 in) and a body length between 6.5–9 mm (0.26–0.35 in). Both sexes have apical third of metafemur and a row of spines along the ventral edge. Another distinctive morphological feature is the pair of small white wedge-shaped spots on the fly’s thorax directly behind its head. The male femur 3 is strongly thickened. It has no basal protuberance. Tergites 2 and 3 have small, pale marks. Female tergites have similar markings, with ocellar triangle bluish-black, metallic sheen. Side margins of thorax dorsum are dusted. Side and hind margins of tergite 4 are not dusted. See references for determination.The eyes of Syritta pipiens span over almost the entirety of their heads. Both sexes have similarly sized hemispherical heads, with a diameter of 2 mm. However, the eyes differ among the two sexes in two ways. First, males have holoptic eyes, meaning that their eyes meet in the front, which is a feature common in male syrphid flies. Second, males have enlarged facets (fovea) between the clypeus and ocellar triangle, which are absent in females.

Taxonomy

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The family Syrphidae divides into four subfamilies: Eristalinae, Microdontinae, Pipizinae, and Syrphinae. Syritta pipiens belong to the subfamily Eristalinae, closely related to the well-known dronefly, Eristalis tenax.

Distribution and habitat

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Syritta pipiens have been found across North American as well as Asia since their first introduction from Europe in 1800s. The species is cosmopolitan except for the Afrotropical realm. It is found wherever there are flowers, as it feeds on and lives around flowers. It is also anthropophilic, occurring in farmland, suburban gardens, and urban parks. It is found in mid April to mid October in Ontario; in Europe, it flies from March to November, as most records show, but it is also likely that it flies all year round in southern European regions where it is warmer. At the larval stage, the species inhabits wetlands that are in proximity to bodies of freshwater such as lakes, ponds, rivers, ditches.

Life history

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Syritta pipiens goes through three adolescent stages – eggs, larvae, and puparia – followed by the fourth life stage of the adult. Larvae develop in moist and rotting organic matter, so different stages of the fly have been found variously in the manures of cows, horses, and guinea pigs, in human waste and decaying heaps of vegetable waste, and in garden compost.

Food resources

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Larval forms of Syritta pipiens feed on decaying organic matter.Adult flies feed on the flowers of water-willow (Dianthera americana L.), white vervain (Verbena urticifolia L.), American pokeweed (Phytolacca decandra L.), and candyleaf (Stevia rebaudiana). They pollinate bluebell flowers (Campanula rotundifolia L.), which is a perennial herbaceous plant, with blue flowers. List of flowers they also visit: Achillea, Allium, Aster, Calluna, Cardamine, Cirsium palustre, Convolvulus, Crataegus, Epilobium, Euphorbia, Galium, Jasione montana, Leontodon, Polygonum cuspidatum, Potentilla erecta, Prunus laurocerasus, Ranunculus, Rosa canina, Senecio jacobaea, Sorbus aucuparia, Tussilago.

Relation to humans

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Flower flies (the family Syrphidae) are critical and one of the most common bio-control agents of plant pests because their larvae feed on aphids. As one of the exceptions, Syritta pipiens specializes in organic waste, leaving the predation to other members of the family.They are also recyclers of plant and animal debris, important pollinators a variety of common plants, as well as pests for certain ornamental plants. Because they play an important role in supporting the functionality of the environment, flower flies also serve as bio-indicators of environmental health, demonstrating the effects of climate change on pollinators. Their abundance is closely linked to agricultural landscapes and arable lands and is contingent upon the density of flowering plants available. Thus, landscape changes can very easily have an impact on the organism’s density, and result in further cascades of consequences.

External links

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Media related to Syritta pipiens at Wikimedia Commons External images Morphology of Diptera