Subject: What’s that Bug (Aquatic Fly)?
Location: South Carolina
June 28, 2016 8:50 am
We found these while doing a stream walk along an urban stream channel in the upper sand hills/lower piedmont of South Carolina. They were found clinging to the underside of the submerged cobble in the riffle sections. Any idea of what they might be? Sorry for the low quality images, but were taken with our phone.
We have been having a difficult time understanding why a winged insect would be submerged under a rock as this insect looks like it would not be aquatic as an adult. It looks very much like some of the winged insects in this posting from our archives that we believe may be Midges with a Fungus Infection, also found near a stream. We are posting your image and requesting assistance from Eric Eaton and our readership. We are further confused because your insect appears to have two pairs of wings, and a Midge would have only one set of wings.
Update: June 30, 2016
Eric Eaton is also unable to provide an identification, but he does agree that it appears to have two pairs of wings, which would eliminate it being a Midge.
Entomologist Julian Donahue responds to our request:
I’m stumped. Body shape looks like a primitive fly (with that small head and short abdomen), but the venation looks more like that of a primitive moth.
I agree that it appears to have two pairs of wings. It doesn’t look like any aquatic insect I know, nor does the venation agree with any aquatic insect I know.
It may be a teneral (freshly-emerged) specimen, and there’s always a chance that it’s a terrestrial insect that got washed into the stream.
Let me know what you find out about this one.
Update: July 1, 2016
In addition to the above possible classifications, we are reminded of some Sawflies regarding the general appearance of this critter. There are many Sawfly images on BugGuide, but Sawflies are NOT aquatic.
Julian Donahue provides tentative identification
On second thought, I’m going to go with my initial gut reaction: a black fly (Simuliidae). Habitat is perfect, body shape fits, and they have broad wings that can fold over giving the appearance of two pairs. It still seems to have too many veins in the wings, but this could be the result of some sort of duplication in the pupa or upon emerging. I still think it’s a teneral specimen, which may account for the odd appearance of the wings.
Ed. Note: Thanks to Julian Donahue’s identification, we are linking to the Black Fly page on BugGuide where they are described as: “black to various shades of gray or yellow; thorax shiny, strongly convex, giving a humpbacked, gnat-like appearance; wings clear, broad, without hairs or scales; heavy veins near anterior wing margin, weak veins posteriorly; small head with large round eyes and short 11-segmented antennae; ocelli lacking.” The habitat is listed as: “larvae develop in running water of all types, from the smallest seepages and streams to the largest rivers and waterfalls; they attach themselves to underwater rocks and other objects by means of small hooklets in a sucker-like disc at the tip of the abdomen.” This BugGuide remark also may be of interest to our readers: “Black flies attack most severely about sunrise and at sunset — either massively and viciously or in such small numbers that they are scarcely noticeable. They bite painlessly so that you may not be aware of having been attacked until small droplets of blood start oozing from your skin. Black flies often crawl into your hairline or through openings in your clothes before they bite you. Therefore, the bites are usually behind your ears, around your neck and beltline, and on the lower parts of your legs. A typical bite consists of a round, pink, itchy swollen area, with a droplet of fresh or dried blood at the center. When the blood is rubbed away, a minute subcutaneous hemorrhage is visible. This hemorrhage and the surrounding pink area become diffuse and larger, and then disappear within a few days. Itching may continue intermittently for weeks, whenever the bitten area is rubbed. Scratching may cause severe secondary skin infections. Toxins injected during an extended severe attack can cause a general illness sometimes called black-fly fever, characterized by headache, fever, nausea, and swollen, painful neck glands. Attacks occur throughout late spring and early summer (sometimes throughout the summer). (Fredeen 1973)(5) often ranked third worldwide among arthropods in importance as disease vectors, but only ~10-20% of the world’s spp. are pests of humans/livestock.”