Syrphinae
Flower flies
The Syrphinae
As larvae the Syrphinae are aphid predators. Females seek out aggregations of aphids on host plants, and lay their eggs among them. The larval flies emerge within days and feast on the aphids for a week or two before they pupate. Larval Syrphinae are very mobile on tiny prolegs, as befitting a voracious hunter of other insects.
Most Syrphinae in North America belong to two Tribes. The Bacchini are relatively small, with abdomen that are straight, narrow and thin or flat. At rest, Bacchini fold their wings straight back over their abdomen, whereas Syrphini tend to hold their wings diagonally away from the body at rest, and usually (but not always) have a rather stout abdomen.
Syrphinae emerge early in spring, and many are migratory; having no nest to return to, they wander and stop wherever they find a dense patch of flowers, feeding and laying a few eggs.
Scaeva pyrastri, Iceberg Point,
Lopez Island