Platycheirus

Platycheirus is a large genus of hoverflies. They are also called sedgesitters.
The genus Platycheirus was established in 1828 by Lepeletier and Serville, with the type specimen of Syrphus scutatus Meigen. This genus is primarily Holarctic in distribution, encompassing 70 species within the Nearctic region. Notably, at least 23 of these Nearctic species are also found in the Palearctic realm, with their approximately 110 species.The distribution of Platycheirus is markedly boreal, with half of the 70 Nearctic species in the Yukon, Northwest Territories, or Alaska. The genus is widespread from Mexico, Central and South America, Europe, Asia, Southeast Asia, Platycheirus are not found in Australia, Indonesia and New Guinea. The genus has a variety of food choices for larvae, ranging from generalized aphid predators to species that specialize in feeding on one or two specific aphid species. Most are feeding within the ground layer of leaf litter.

Characteristics

For terminology and a key to European Syrphidae see Speight.
Platycheirus are slender, small to medium-sized flies that are often covered in fine hairs. They are mostly black or metallic green, and they may have yellow, reddish, or whitish-yellow spots on their abdomens. These flies do not have any bristles.
The head of a Platycheirus is somewhat rounded and is usually a bit wider than it is tall. It is also slightly wider than the thorax, with a small indentation at the back. The epistoma, which is the lower part of the face, is black and has a central knob. The face is often slightly recessed and has a small bump. The upper edge of the mouth is slightly extended.
The antennae are placed high on the face, above the middle, and the third segment of the antennae is longer than it is wide. The arista, which is a part of the antennae, is thickened in its base and has tiny hairs. The eyes are smooth and are holoptic in males, meaning they meet in the middle. The wings have a cross-vein located before the middle of the discal cell. There is a distinct but not very strong spurious vein.
The legs of Platycheirus are somewhat slender. The hind metatarsi are thickened and show secondary sexual characteristics in males. This means that the front tibia and tarsi of males can be dilated in various ways and may have special colors. Sometimes, only the tarsi are dilated.
Males can be identified by their legs, especially the front legs. Some females have unique markings that help with identification, but many females are harder to identify, and some may even be impossible to distinguish.

Species by subgenus

Subgenus: Carposcalis Enderlein, 1938
Subgenus: Eocheilosia Hull, 1949
Subgenus: Pachysphyria Enderlein, 1938
Subgenus: Platycheirus Lepeletier & Serville, 1828
Subgenus: Pseudoplatychirus Doesburg, 1955

P. glupovi Barkalov, 2007
P. peteri Doesburg, 1955

Diagnostic keys

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Platycheirus.fulviventris.-.lindsey.jpg|Platycheirus fulviventris male
Platycheirus peltatus.jpg|Platycheirus peltatus male
Platycheirus.clypeatus.-.lindsey.jpg|Platycheirus clypeatus male
Plat.manicatus.jpg|Platycheirus manicatus male
Platycheirus.splendidus.-.lindsey.jpg|Platycheirus splendidus male
Plat. albimanus.jpg|Platycheirus albimanus female
Platycheirus manicatus.jpg|Platycheirus manicatus female
Platycheirus.occultus2.-.lindsey.jpg|Platycheirus occultus female