I was just about to post about these nasty buggers.
We were in a cabin from for memorial day weekend and didn't have a clue about them. I immediately acquired a "pet" and thought nothing of it until I was stung. Then the cable repair guy came by and said "oh, that's a yellow fly" and didn't tell me just how nasty they are.
After a day, I suddenly started itching and thought it was a mosquito bite. The next day I was at the pool and again, the flies were around me, and I finally jumped into the pool to get rid of them. Ditto the day after.
It wasn't until the day we were to come home I realized how many bites I had, but still, they didn't itch too badly. Until I got home, and then they started up in full force.
I've been home since Wed night, and have more than a dozen of these bites, and can honestly say I have never experienced itching like I did. The earlier bites are clearing, but the more recent ones still itch, and my legs look diseased. I'm apparently allergic to the bites, but not as bad as the poster above mentioned. Still, the welts are very large, and they did open up an ooze a bit. Neosporin is helping, as they don't seem quite as red today.
Disney could have warned us about the problem this year. They did have a note in the cabin about the black bear siting - it wouldn't have been a terrible thing to warn people to get indoors if they're being attacked by those nasty flies.
I can say that I will probably never go to WDW in May again - or if I do, stay away from the Fort.
I wish I had seen this post before I left.