They're probably fungus gnats. The little flies are the adult form. They hang around the surface of the medium most of the time where they live for about two weeks while breeding, laying eggs, and completing the fungus gnat life cycle. Those in the larval stage are tiny little worms that live in the potting medium. The larvae mostly eat decaying bits of medium, but that does not necessarily mean your medium is rotted. In organic mediums, the decay process is already underway to some extent even as it comes out of the bag after you buy it, so the worms don't have to wait. The larvae also feed on the roots of at least some kinds of plants. Fungus gnats multiply rapidly and can become a real nuisance to those growing orchids or potted plants. One control method is to hang yellow sticky cards around to catch the adults, but a much better solution is to kill the larvae. The most effective way to do that is with a bacterium called Bacillus thuringiensis subspecies israelensis. It's easy to find and easy to use. Just go Lowe's, Home Depot, or a garden center and buy a pack of mosquito dunks. They have that bacterium in them because it's also effective against mosquito larvae. You can float one of the dunks in a bucket of water for a day or two and then draw from it to water the orchid. You can add more water to the bucket as needed. The dunk will still be good until it's gone. You will start killing the larvae right away. Subsequent waterings will get those that hatch later. The bacterium is not dangerous to humans, animals, or plants.

Ah, bullrush! Thanks! Last year we had the worst infestation of gnats in the house. It was horrible! We tried all sorts of sprays, fly papers, pouring bleach down the drain, getting rid of all produce unless refrigerated, blah. Finally, I got some small decorateve jam jars (from the canning section at Walmart) and put in a bit of apple cider vinegar. I popped a few small holes into the lids and set them about the house. The gnats would climb into the holes to get the vinegar and get trapped in there and drown. After a week, they were down by half. After 2 weeks, not a single live gnat could be found. :-D

I found this online..."Despite their common names, crane flies do not prey on mosquitoes as adults, nor do they bite humans. Some larval crane flies may on occasion feed on mosquito larvae. [1] Adult crane flies feed on nectar or they do not feed at all; once they become adults, most crane fly species live only to mate and die. Their larvae, called "leatherjackets", "leatherbacks", "leatherback bugs" or "leatherjacket slugs", because of the way they move, consume roots (such as those of turf grass) and other vegetation, in some cases causing damage to plants. Therefore the crane fly is occasionally considered a mild turf pest in some areas. In 1935, Lord's cricket ground in London was among the venues affected by leatherjackets: several thousand were collected by ground staff and burned, because they caused bald patches on the wicket and the pitch took unaccustomed spin for much of the season.[2]"

When I used to get a lot of bites on my arms at the lake I'd just go to the pump and pump some nice cold well water on my arms and it was so soothing. Also soothing because it was usually warm and I'd be sweaty. I wonder if the perspiration and/or the other stuff on the skin was an irritant to them too but just plain water helps me. I do it to this day if I get a lot of bites. If they're all over I'll take a shower. Plus just avoid scratching. And of course, move to where there's fewer mosquitoes as a proactive step. Don't like skeeters.