What's That Bug? does not endorse extermination

Subject:  Bug in freshwater fountain
Geographic location of the bug:  Victoria Australia
Date: 02/07/2018
Time: 05:00 PM EDT
Your letter to the bugman:  Hello,
We have a fresh water pond with running water along a pot. This is at the top of the pot and these hanging in the water. Fixed by their back end, hanging down, and with two antennae like.
They are 6-8mm in length and in a group of about 20!
They seem the wrong shape for the mosquito larvae I have seen, but not sure if they are!
Thanks for your help
How you want your letter signed:  Julien

Black Fly Larvae

Dear Julian,
Your query has us quite intrigued.  We concur that these are NOT Mosquito Larvae.  Mosquito Larvae breathe through a siphon and they congregate at the surface of generally stagnant water.  We suspect these are larvae and that they are members of the Fly order Diptera.  We also suspect that in their natural environment, they affix themselves to rocks in flowing streams.  We located this image on SlideShare of some aquatic Dipteran larvae and several resemble your individuals.  At this point, we suspect this might be a member of the Black Fly family Simulidae, and according to BugGuide:  “Larva: brown, gray, or black with light brown head; body cylindrical, somewhat club-shaped; head with prominent pair of mouth brushes used for filtering food from the water” and “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.”  Bug Eric has some very similar looking images.  Though they are not Mosquitoes, female Black Flies are blood suckers.  According to BugGuide:  “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)  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.” According to Atlas of Living Australia:  “Most black flies gain nourishment by feeding on the blood of mammals, including humans, although the males feed mainly on nectar.”

Black Fly Larvae

Dear Daniel,
Thank you so much for looking into that!! Your suggestion and pictures are very convincing. We do have these flies around as well. I have taken pictures again and I think that we can see the one in their cocoon on the bottom and the other one on top!
Your site is a great help!
Best wishes
Julien

Black Fly larvae and pupae

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What's That Bug? does not endorse extermination
Location: Victoria, Australia

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