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Genus Toxomerus

Syrphid Fly - Toxomerus marginatus - female Another Syrphid Fly - Toxomerus geminatus - female What is this? - Toxomerus politus - male syrphid fly, yellow legs - Toxomerus Toxomerus marginatus? - Toxomerus marginatus Toxomerus? - Toxomerus marginatus Maybe Toxomerus? - Toxomerus geminatus - male Unk Dipteran (Tephritidae?) netted on Centaurea stoebe - Toxomerus marginatus
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Diptera (Flies)
No Taxon ("Aschiza")
Family Syrphidae (Syrphid Flies)
Subfamily Syrphinae
Tribe Toxomerini
Genus Toxomerus
Explanation of Names
Toxomerus Macquart 1855
From Greek toxon 'bow' + meron 'thigh' (refers to the bow-shaped hind femur)
14 spp. in our area(1)(2)
5-13 mm
Pattern on abdomen is characteristic(3); look for a v-shaped notch on the back margin of the eye.
In identifying the most common eastern species, consider the margin of the abdomen. If continuously yellow (sometimes narrowly so) you've got T. marginatus. If it is alternating black and yellow because the dark horizontal bands extend all the way to the edges, T. geminatus (scutellum dark with sharp yellow border) or T. politus (scutellum light). --Steve Pelikan
Guide to common spp.:

Further south, esp. in Florida, there are more species and identification from images is much more difficult (perhaps impossible)
Colors vary with overall temperature during pupation: if it was hot, the yellow/orange increases and the background becomes lighter, but if it was cold, the dark/black increases and the yellow/orange becomes darker like the background.
"extremely diverse in the tropics with many, many undescribed species and over 100 described species. In Florida, there are 10 species of Toxomerus: T. arcifer, T. boscii, T. corbis, T. dispar, T. floralis, T. jussiaeae, T. geminatus, T. parvulus, T. politus and T. marginatus. It is necessary to see characters on the hind leg of the male, a good lateral view, and wing microhairs to identify Florida specimens to species." --Jeff Skevington
T. marginatus: much of the US & so. Canada; common
T. geminatus: e. NA; common
T. politus: so. Canada to Argentina; uncommon
T. occidentalis: w. NA; common
10 spp. in Florida
Life Cycle
Eggs are laid singly on plants near aphids. Presumably late-instar larvae overwinter. Pupation is in soil cavities in spring; adults emerge in summer.(3)
Egg laying
See Also
Internet References
Works Cited
1.Key to the genera of nearctic Syrphidae
Miranda G.F.G, Young A.D., Locke M.M., Marshall S.A., Skevington J.H., Thompson F.C. 2013. Can. J. Arthropod Identification 23: 1-351.
2.Toxomerus mutuus
3.National Audubon Society Field Guide to Insects and Spiders
Lorus and Margery Milne. 1980. Knopf.