I stopped a student who was entering the library with a plastic bag full of fast food. I politely asked him to leave the food on a rack next to our counter and he could collect it on his way out. He looked suspiciously at the rack.
Him: Are there any cockroaches here?
Him: What about ants?
Me: No, and we hope to keep it that way by not having food in the library.
Him: But I wasn't planning on eating it here!
Me: *silently bashing head against wall*