Eastern Hornet Fly

The Eastern Hornet Fly (Spilomyia longicornis) is a large, yellow-and-black, Nearctic flower fly. A convincing wasp mimic. In addition to being a visual mimic, the Eastern Hornet Fly mimics the behavior of wasps as well, wagging its abdomen up and down, flicking its wings, and waving its dark-colored front legs as if they were long antennae. The unusual eye coloration and patterning, dark spots and blotches overlaying a light background, is characteristic of this species and other species in this genus. Larvae are dendrolimnetobionts, obligate rot-hole inhabitants.

Flight season: August and September

Flowers: More often observed perched on leaves at the edge of woods rather than at flowers, however, it is known to visit asters and goldenrods.

Similar species: Spilomyia alcimus, Somula decora, Sphecomyia vittata, and Temnostoma alternans, which are all yellowjacket mimics.

Field notes: There exists a curious intersection here, between language and mimicry, as the species name “longicornis” refers to the Longhorn Beetles. My guess is that Loew, who assigned the name in 1872, had the Locust Borer in mind, a beetle that has a somewhat similar yellow-banding pattern. Expressed in terms of what it is not, the name draws attention to the convergent evolution of mimicry.

Common Bog Fly

The Common Bog Fly (Parhelophilus laetus) is a medium-sized, orange-colored, Nearctic flower fly. Adults have a pair of stripes on the thorax often with a thin center stripe between them. The hind femur is mostly orange with a black band around the middle. The adults are commonly found perched on grass blades near the shorelines of ponds and wetlands. The larvae have long breathing tubes which allow them to live in low-oxygen waters thick with decaying organic matter.

Flight season:

Flowers: ?

Similar species: Helophilus sp. and Lejops sp.

Dusky Bog Fly

The Dusky Bog Fly (Parhelophilus rex) is a medium-sized, dark-colored, Nearctic flower fly. Adults have a pair of thin gray stripes on the thorax. The hind femur is almost entirely black. The larvae have long breathing tubes which allow them to live in low-oxygen waters thick with decaying organic matter.

Flight season May – July

Flowers: Willow catkins

Similar species: Parhelophilus obsoletus and Helophilus sp.

Parhelophilus rex
Parhelophilus rex – St Louis County – June 2, 2017

Eastern Catkin Fly

The Eastern Catkin Fly (Brachypalpus oarus) is a large, infrequently-observed, Nearctic flower fly of old woodlands. Usually observed hovering near or perched on sunlit tree trunks. An imperfect mimic of large mining bees. When perched on a tree it resembles robber flies of the genus Laphria. The body is covered with long, yellowish hairs. The face of the female is triangular in shape. The larvae live in rot holes in deciduous trees. Length 10 – 14 mm.

Flight season: April – May

Flowers: Catkins?

Similar species: Chalcosyrphus inarmatus

Brachypalpus oarus
Brachypalpus oarus (male) – Rice County – April 17, 2017

Meadow Sedgesitter

The Meadow Sedgesitter (Platycheirus quadratus) is a small, dusky-yellow and black, Nearctic species. Males can be identified by abdomen pattern and flattened front tibia and tarsi (see drawing). Females, patterned similarly to the males, are not easily separable from other Sedgesitter (Platycheirus) species. Adults are commonly found on grass and sedge blades at the edge of ponds and wetlands where they feed on pollen grains.

Flight season: June – September

Similar species: Melanostoma mellinum and other Platycheirus species


Western Roundtail

The Western Roundtail (Melanostoma mellinum) is a small, dusky-yellow and black, holarctic species. Identifiable by abdomen pattern. Males lack the flattening or broadening of the front legs characteristic of similar Sedgesitter (Platycheirus) males. Adults can be found on leaf surfaces where they feed on the pollen of grasses (Poaceae) and other wind-pollinated plants but also visit a variety of flowers. Larvae are entomophagous, mainly aphids.

Flight dates: April – July

Flowers: Rue Anemone, Dandelion, Wild Plum

Similar species: Platycheirus quadratus



Long-nosed Swamp Fly

The Long-nosed Swamp Fly (Lejops lineatus) is a small, gray, yellow, and black, Holarctic species. Unlike most other Syrphidae, female and male eyes are separated. Males have thinner abdomens and are the more colorful. The larvae have long tails and are found in wet areas with decaying vegetation at the edge of ponds and other wetlands.

The taxonomy of this species is a little messy. In Europe it’s Anasimyia lineatus. Here it’s Lejops lineatus or Lejops (Eurimyia) lineatus or Eurimyia lineatus. The common name, Long-nosed Swamp Fly, simplifies the problem.

Flight season: May – July

Flowers: Sweetflag Iris, Spiderwort, Creeping Thistle

Similar species: Lejops bilinearis and Parhelophilus sp.