Or: how to waste a sizable chunk of your evening.
Flies are odd creatures, and often kind of annoying too. I can deal with the really small ones you barely notice unless you get a close view, but anything that makes a sound gets on my nerves really quickly. Whenever one gets into my room I have to spend the next hour getting that thing out. Sometimes you can get away with opening the door and “shoo”-ing it out, but that won’t help your cause if there’s a dozen more swarming in the hallway. So what then? You have to catch it. I recommend Nest Balls for the best catch rate, or if those aren’t available use Ultra Balls. (Master Balls are way rare, don’t bother wasting them on this.)
Seriously though, over the years I’ve picked up some neat tricks you can apply to almost any fly-catching situation. Though success is never guaranteed, your chances of victory will certainly be improved.
If the fly has positioned itself on a window, and you can pull curtains or something similar in front of it, do so. In most cases the fly can’t come out and will be dead the next morning. Not the most humane way, but sometimes drastic measures need to be taken.
Here’s a cool one you could also use as a party trick of sorts. Because hey, catching a fly with a single hand is pretty impressive! Flies already have the tendency to fly straight forward for a little bit after liftoff, and even more so when you’re coming in from behind. Use this knowledge of the fly’s first moment of aerial movement to your advantage: aim the cup (or whatever you’re attempting to capture it with) a bit in front of it and move in from its rear. Or, as I said in the example above, you can use your hand to grab it just as it takes flight. Be careful not to squeeze it too hard though, your hand will get messy and it’s kind of cruel.
As for locating them once they’ve buzzed past you, your best bet it your hearing. Try to listen for that small distinctive sound, and sometimes even tapping against windows. If your unwelcome guest doesn’t make any noise, you’re out of luck. Have decent eyesight and hope you get a chance to spot it.
Hope this helps. Good luck out there soldier.