When I was doing research on the effects of irradiated fruit on fruit flies, I would have to anesthetize a pickle jar full of them, then count them one by one before they woke up. Putting them in the freezer for a few minutes really slowed them down, but these weren't flightless (well until the 6th generation or so), so if you weren't fast they would be every where haha and then I would have to fog the place do they wouldn't mix with the control cultures haha. I started that research in high school and people would walk down the hall with swarms of fruit flies the first couple times I tried.