Every spring, we get an odd fly buzzing around the house, which is twice as big as the 'normal' ones, so I figure it's from last year and coming out of hibernation. We generally wait for it to come to our glass back door, let it out, and that's the end of it. We have screens on our windows, so the rest of the year we maybe see five flies total. Or maybe a dozen. But not more than that. Last night I saw one of those, thought 'oh, again', let it out, and thought that was it. By tonight, I have killed 20 more, big ones and gigantic ones, and a few normal sized ones. This is really, really unusual. Anybody have a thought about what is going on? I never had 21 in the house at any one time. It's only 2-3, and 5 once after spending 6 hours outside of the house. It feels like they are slowly coming out of somewhere one by one. We do leave the porch door open from time to time, but I don't see 21 flies coming inside in a single 15 minute open door session, and I definitely did not have 21 last night. The weather did not change much since two days ago. I wasn't cooking either. Any ideas? I find flies gross, and it's beginning to freak me out. Every weird noise sounds like a fly buzzing or hitting a wall. Every light feeling on my skin feels like a fly walking on me.