Identification
scutellum brownish, yellowish, or diffuse mix of both; abdomen with thin but continuous yellow margin; tip of abdomen pointed in female, rounded in male; top of thorax bronzy-brown with yellow margin; wings clear; eyes large, reddish-brown
Range
most of United States and southern Canada
Habitat
adults often found visiting flowers of herbaceous plants or shrubs
Season
adults from April to November
Food
Adults feed on nectar and pollen. Larvae are voracious predators of aphids, thrips, small caterpillars.
Remarks
Considered beneficial insects, because they are predatory on many plant pests. This
article suggests that they and other syrphids are more efficient at pest control in sheltered sites.
When the pupa is exposed to heat, the adults look very pale and orange, if they develop under cold conditions, they turn much darker, sometimes nearly completely black. (Comment by Martin Hauser)
See Also
Toxomerus geminatus is similar but scutellum blackish with well-defined yellow margin, and margin of abdomen alternately black and yellow (i.e. lacks thin yellow marginal strip)
(
compare images of both species)
Internet References
Picture at Systematic Entomology Laboratory site.
live and pinned adult images plus related species, with arrows pointing to diagnostic field marks (Jeff Skevington
et al, Field Guide to Flower Flies of Ontario)
