Fungus gnats look like fruit flies, but aren't interested in vinegar or other fruit fly traps. They can also be distinguished by their catlike ability to spring

Fungus gnats look like fruit flies, but aren't interested in vinegar or other fruit fly traps. They can also be distinguished by their catlike ability to spring back from a slap with "excuse me, I was flying here, do you mind?" insouciance. I've had success suppressing them with frequent sprays of neem oil, direct to the soil of the pots. Daily for a week or two to break the life cycle and then weekly or more often to keep the inevitable survivors knocked back and feeling unwelcome. They're also suckers for a candle left lit in a darkened room.