1. Where fruit flies come from: Female fruit flies lay their eggs on just-ripening produce — like fruits and some vegetables, fresh from the grocery store. Then as the fruit continues to ripen and, eventually, rots, the eggs hatch and the fruit flies (adult and baby) burrow into your apple or peach — or potato or onion — in search of the bacteria and yeast they need to feed on. Fruit flies, which prefer warm, moist environments and have a natural lifespan of about 40 to 50 days, reproduce quickly; it takes only one week for them to reach sexual maturity. And a single pair of fruit flies can produce hundreds of little baby flies in a matter of just two weeks, and then, within a week, those offspring can produce babies, and so on, and so on, until your kitchen is fruit-fly crazytown and you’re tempted to contact air traffic control.