Familiar visitors: Fruit flies move indoors

I suppose I should look upon fruit flies as old friends. Our formal introduction took place in junior high school, in science lab. Now they visit regularly, every late summer and early fall.

Still, for old friends, they can be bothersome. No, they don’t bite, but I’d rather do without their flitting around any ripening fruit in the kitchen.

Egg-laying right on schedule

As it turns out, fruit flies don’t really turn up this time of year; they just make their presence known. All summer they’ve been hanging around outdoors, attracted there, as they are indoors, to ripe and overripe fruits. Cooling temperatures drive them indoors. An abundance of ripe and overripe apples, tomatoes, pears and other fruit, much of it now brought indoors, provides further enticement for their move.

It’s actually fruit flies’ larvae — small, white maggots — that are feeding on the fruits. After feasting for five or six days, larvae are transformed into the all-too-familiar flies. The females do more than just flit around for the few days they are alive; they fly up to six miles and keep busy laying eggs — up to 2,000 of them. The eggs hatch into maggots, which feed, become adults, and round the cycle goes, leading to skyrocketing populations of maggots and fruit flies.

Swat them

To control fruit flies, start by regularly discarding overripe fruit. It also helps to clean kitchen sink drains, where bits of fruits or their juices may lodge.

You could, of course, bypass the whole problem by not having any ripe fruit indoors except in the refrigerator. We gardeners know, however, how cold deadens the flavors of garden-fresh fruits, and even ruins the flavors of some, such as tomatoes and bananas.

Fortunately, some simple devices can help in the war against fruit flies. There’s some primal satisfaction in just swatting at them with a rolled-up, wet facecloth, or you could go a little more high-tech and vacuum them up right out of the air. Both of these methods must, of course, be kept up on a regular basis.

Trap them

Traps take less participation. For the simplest trap, just set out a glass of wine to which some dish detergent has been added — and be sure to label the glass so no one drinks the liquid. After landing on this liquid for a drink, fruit flies become wetted and are unable to take off again. Another trap capitalizes on fruit flies’ low intelligence: A funnel set spout down over the opening of an upright glass filled with bait provides easy entry but clever exit, too clever for fruit flies.

A number of commercial traps, such as the Contech “Fruit Fly Trap,” work on these same principles and are also effective.

Newly emerged fruit flies are attracted to light, a habit that can lead to their undoing. Shade all the windows in your kitchen except one, and leave only a crack of light coming through the bottom of that window. Put a baited dish near that opening, wait awhile, then rush the dish, with attendant flies, outdoors.

On the same theme, darken with paper or dark paint the upper third of a one-quart jar, then coat the inside of the jar with something sticky such as honey or vegetable oil. Invert the jar, raised off the counter with some small blocks of wood, over some bait. Flies will feed and then fly up toward the light, where they will be trapped.

The flies are attracted to yeasts that cause fermentation, so any piece of fruit, even yeast and water, are suitable bait. Or you can mix up a feed of mashed bananas and agar, just as I did when rearing fruit flies in junior high school science class.