Syrphini
Genus Dasysyrphus (Syrphini)
A holartic genus found in Europe as well as North America as far north as Alaska. The abdomen has distinctive pale markings and a shallow groove runs around its margin. The wings are iridescent from fine tiny hairs (microtrichose) and there are fine hairs on the eyes as well. At least 13 species of these flies are recognized in North America, but only one species has been identified thus far in the San Juan Islands.
Genus Eupeodes (Syrphini)
A holarctic genus distinguished by a pale face, relatively flat abdomen with pale markings, and iridescent microtrichose wings. Only one species is recognized in North America, popularly called the Bird Hover Fly. It is widespread, abundant, a voracious predator of aphids, and can reproduce several generations each summer. Males have large protruding genitalia.
Genus Scaeva (Syrphini)
This Old World genus is represented by a single species in North America that is widespread and abundant, and presumably introduced. It is very difficult to distinguish from an abundant native species, Eupeodes volucris. Look for a halo of fine pale hair around the eyes. The eyes of Eupeodes are hairless. Larvae pupate within a few weeks, and adults over-winter in the leaf litter. Scaeva cannot survive severe winters but they quickly re-colonize northerly latitudes each summer.
Dasysyrphys intrudens,
American Camp, San Juan Island
Eupeodes volucris, Lopez Island
Genus Epistrophe (Syrphini)
This genus is most abundant on the east side of the continent; however, three species have been collected in the Salish Sea region and the islands. The paired yellow markings meet seamlessly in the middle, the eyes are not haired, and there is no dark marginal line around the abdomen. These flies may be confused with Syrphus, Metasyrphus and Parasyrphus, but their markings are divided by a dark reddish margin or a wide gap.
Genus Chrysotoxum (Syrphini)
This beautiful flower fly is a Vespula (”yellowjacket”) mimic with distinctively elongated antennae and a nearly hairless body that make it appear more wasplike. Two species have been recorded in the Salish Sea, of which only one has been documented thus far in the islands. Like most of the larger Syrphini, it is most likely to be seen feeding on large composite flowers. Larvae are presumed to be aphid predators but little is known about them.
Scaeva pyrastri, Lopez Island
Genus Fazia (Syrphini)
An unusual flower fly genus with only one North American species, Fazia superficially resembles other small slender flies such as Sphaerophoria; look for four tiny diamond shaped marked at the end of the abdomen. Larvae hunt aphids in trees and on the ground, and over-winter in leaf litter before pupating the following spring. They may produce several generations each summer.
Chrysotoxum fasciatum,
American Camp, San Juan Island
Genus Syrphus (Syrphini)
These are cosmopolitan flies with 14 species in North America from coast to coast and Texas to Alaska. Some species are also found in Europe and Asia. Four species are recorded in the Salish Sea, at least two of them in the islands. Although patterns are bold and conspicuous they are also highly variable. Wings are microtrichose, and the pairs of yellow markings are separated by a faint reddish midline. Many Syrphus are multivoltine, producing several generations each summer, and are known to feast on gall-forming aphids as well as free-living aphid species.
Epistrophe grossulariae,
American Camp, San Juan Island
Genus Metasyrphus (Syrphini)
Formerly a subgenus of Eupeodes, these flies are now recognized as a separate genus. Six species have been collected thus far in the San Juan and Gulf Islands. Paired markings are separated in the middle by a gap or reddish margin, like Syrphus, but there is also a conspicuously dark equatorial line around the abdomen. Like other Syrphini, it is most likely to be seen on yellow flowers.
Fazia micrura,
Iceberg Point, Lopez Island
Syrphus opinator, Friday Harbor,
San Juan Island
Syrphus ribesii, Blind Island
Genus Sphaerophoria (Syrphini)
A widespread, common circumpolar genus of small, slender flies with long narrow abdomen and three bold yellow bands. Six species are recorded in the Salish Sea, three in the islands. Males have conspicuous globular genitalia at the tip of their abdomen. Larval flies feed on aphids, mainly at night, and at least some species are migratory and produce several generations each summer (multivoltine).
Metasyrphus fumipennis,
American Camp, San Juan Island
Sphaerophoria sulphuripes,
Lopez Island