Eristalini
Genus Eristalis (Eristalini)
Eristalis proper is an Old World genus with only a single introduced North American representative, the so-called European Drone-fly. The abdomen is boldly marked in orange, and the face and thorax are covered in fine pale hair. Often seen visiting gardens, this noisy fly lays its eggs in puddles and ditches, even in watering cans, producing squirmy rat-tailed larvae.
Genus Eoseristalis (Eristalini)
A sub-genus of Eristalis with some Holarctic species (such as E. arbustorum) and others that are endemic to North America, these “dawn-flies” (from the Greek eos, “dawn”) are easily confused with Eristalis tenax, but are more metallic and less visibly hairy. They are poorly documented in the Salish Sea as a whole. Recent surveys have found seven species in the San Juan and Gulf Islands.
Genus Eristalinus (Eristalini)
Introduced from Europe, this dark metallic fly is now widespread in North America, and is easily recognized from the pattern of dark spots on its gray eyes. Eggs are laid in stagnant ponds and ditches, also brackish coastal lagoons; like many other hover flies it prefers composite flowers.
Eristalis tenax, Lopez Island
Genus Helophilus (Eristalini)
A large bold fly with a striped thorax and bold yellow abdominal markings similar to those of the European drone fly, Eristalis tenax. It is also similar to Lejops, but lacks the protruding snout typical of that genus. “Helophilus” is Greek for “marsh lover”, and indeed this fly lays its eggs in shallow wetlands, rich in organic detritus. Its rat-tailed larvae are filter feeders.
Eoseristalis arbustorum, Lopez Island
Genus Mallota (Eristalini)
This stout fly is a hairy bumblebee mimic with adensely hairy head and thorax similar to Criorhina.
Eggs are deposited in pockets of water in rotting logs; larvae are deposit feeders. Male flies are known to congregate at high points where they wait for females (“hill-topping”). Mallota can be distinguished from other bumblebee-mimic flies by their facial tubercle (like a bump on the nose) and enlarged femora on their hind legs.
Eristalinus aeneas, American Camp,
San Juan Island
Genus Sericomyia (Eristalini)
At least four species of these stout flies are found in the Salish Sea and the islands, of which this is the most often seen. It has three pairs of straight yellow bands on its abdomen and the hairy arista (antennal knobs) that are typical of the Eristalini. Eggs deposited in wetlands hatch into deposit feeding rat-tailed larvae. Adult males reportedly engage in “hill topping” congregations to attract mates.
Helophilus fasciatus, Lopez Island
Mallota sackeni, Lopez Island
Sericomyia chalcopyga,
Lopez Island