Insect Order Diptera (True Flies)

I've been looking around the web to find out what they are and I saw a site that said they were drain flies? It makes sense to call them that but what are their true name? It can't be drain flies can it? Anyway they are taking over my tank. They start out like 1cm long white inch worms that have a black tip on the face and tail, they then form a brownish-black shell, like a cocoon and then they turn into tiny flies the size of a gnat or fruit fly and they don't die under water they are water proof. I hate to say it if you guys are bug lovers but they have to move out, possibly to the swampy stream out back. Does anyone know their name and if they are harmful to goldfish at an epidemic rate? They breed like crazy and I can't keep up.

are midges and gnats different bugs? if so, how? am tying midge larvae and pupae, and buying Griffith's Gnats and wondering if it's all in the family.

says here midge pupae rise in the water and struggle in the film to become adults. my imitations are so small that they don't seem to go down very far in order to rise--ike a wet fly might at the end of the swing. any ideas? or am i fishing them wrong?

in the air over the stream last night was a cloud of "midges", all floating in pairs. the hundreds of pairs looked like little colons (:), little black dots keeping a constant distance. you had to see it to believe it. mating dances? has anyone else seen this?

river: Little Juniata, PA
water temp: 62 degrees
air temp: high 70s
time: twilight

This is a spin-off from a tangent in another topic which seems worthy of its own thread.

I wrote about the midge I photographed:

I'm not sure how a griffith's gnat is supposed to imitate such a thing

Gonzo replied:

Schwiebert's theory was that when it was awash in the film, the herl and halo of hackle suggested the loosening pupal shuck around the dark body of the emerging midge. Others have speculated that it imitates a cluster of midges. Both theories are reasonable, I suppose, depending on the size of the Griffith's Gnat that is effective relative to the size of the actual midge. Like many anglers, I just know that it does work. :)

Those are the explanations I've heard, too, but I'm skeptical of both. I'm not doubting the effectiveness of the Griffith's Gnat; I just think people have traditionally stretched the bounds of credibility when trying to explain a fly's success in imitative terms, and this is one of the more prominent examples.

Has anybody here seen a cluster of midges on the water? I haven't. I have seen midges thickly grouped on rocks next to the water, and I don't doubt that they occasionally fall off of there, and probably sometimes two are three are clinging to each other. I've also seen early-season stoneflies balled up with each other in an opaque little (presumably mating-related) clump on a midstream boulder, and I wouldn't be surprised if some midge species do something like that too. But trout don't see balls of midges floating around very often on any stream I've ever observed. Has anyone experienced that?

In either case, I can't see something so opaque as a Griffith's Gnat effectively imitating what would surely be a loose ball of gangly entangled midges. You would have to roll them around in your fingers for a while to goo them together so solidly.

I just can't see the herl and hackle imitating, or even suggesting, a loosening pupal shuck. Shucks don't get that loose. They trail behind length-wise; they don't balloon to the sides. And they aren't pointy. Of course I'm sure Schwiebert knows all that and was just trying to add an idea to the mix of explanations, but I do find that one as far-fetched as the others.

Here's another far-fetched guess: maybe the hackle and refractive trickery in the surface film reduce the perceived thickness of the fly and it passes for a single midge pretty well. This could be tested in an aquarium but it's late and I'm feeling lazy.

I think it's more likely that when trout take a Griffith's Gnat they're only looking for (at most) the right general size and color. It's not as fun, but sometimes things are really that simple.