I was over by the door, saw a fly, finally remembered to look at security camera footage. The IR was on.
Looks like a streak. Like light, but not like an orb.
So yes, you can see flies on IR. At least small ones, don’t look like an orb. You’ll barely see it though, and without IR, would be hard to see most likely.
I could upload the video, but I’m lazy, and in it.
No idea what they look like closer on the IR though.