How I stopped worrying and learned to love my fruit flies

Close-up on Drosophila melanogaster, the common fruit fly. Photo by Sanjay Acharya

One of the trivial hardships of summer in North America, along with poison ivy (or oak, or sumac), sunburns, and a spoiled half of a watermelon taking up good refrigerator space, is the fruit fly: Drosophila melanogaster.

The fruit fly’s greatest weapon may be that it, in small numbers, it is easy to ignore. In the early days of summer, five or six little flies swarming around a bunch of bananas or your freshly opened bottle of merlot is almost festive.

But much like the cuteness of kittens, which ensures that humans will always be slaves to cats, this is one of nature’s little ploys. Fruit flies show up in small, harmless-looking groups — maybe on the back of a cantaloupe or some fruit from the farmer’s market. But they are experts at exploiting small spills and other little bits of chaos in your kitchen.

There are the obvious culprits, like any kind of fruit or vegetable, especially rotting bananas and potatoes — even a small, forgotten grape hiding behind the blender. There are also places where clouds of flies can be visible: around empty bottles or cans sitting in a recycling bin, or the bottom of the recycling bin itself.

Moisture and some nutrients — that’s all that is needed to support exponential population growth.

Let’s say that half of your little squadron of six flies are sexually mature females, capable of laying eggs. That’s three flies laying up to 100 very very small eggs daily on whatever overripe fruit or vegetables they can find for their entire lifespan! In a bit of good news, Drosophila’s lifespan is comparable to that of a pop song: a week and a half. But the math is not on your side; over the course of ten days, three flies can lay something like 3,000 eggs.

And the twilight of this first pioneering generation of brave fruit flies — full of documentaries and retrospectives on the challenges they faced, their romances, their untimely deaths, wars they fought with very small spiders — sees the sun rising on legions of their spoiled brat offspring. On that first day that you noticed some flies, they were already laying eggs. Ten days later, those eggs have produced mature offspring — as many as 300 new flies can pop up every day for the next week. If you do nothing, you can have 150 flies laying 100 eggs a day over the course of a week.

But most of us are not going to see a swarm of 300 flies in the kitchen and say “How festive!” or “No worries, I’m sure they’ll be gone in a few months.” I am, admittedly, imposing my own anti-swarm cultural bias here, but the seasonal popularity of the Google search “fruit fly trap” suggests that most of us will go to war against the invader.

Like crash diets and cargo shorts, interest in fruit fly traps comes and goes with the seasons

The standard means of eradicating fruit flies are well known:

· Apple cider vinegar in just about any container with a small opening. (The bug-murdering entrepreneurs at TERRO sell smart little tomato-shaped fruit fly traps, but a bowl of cider vinegar covered in plastic wrap with toothpick holes in it does the same job.)

· Other people use water with a little sugar and a little dish soap in it — the soap adds just enough tension to the surface of the water that it traps the flies.

· Aerosol insecticides work against the adults, but fruit flies scatter very quickly and are tough to see in flight. This leads to diminishing returns, particularly in the kitchen, where there always seems to be a fork or plate or other surface exposed that is incompatible with a patina of insecticide.

· Pouring boiling water down drains to kill eggs laid in the goo that lines all kitchen sink pipes.

And you may be able to wipe out huge numbers in a given generation. Optimistically, let’s say you’re successful in destroying 90 percent of the fruit flies that emerge in a day. You’re still not going to catch up unless you are successfully getting rid of the eggs.

Ultimately, what is needed is “the nuclear option”: release the obsessive-compulsive Kraken you keep chained up in your brain. Your OCD self will revel in the opportunity to clean every surface every few hours, wrap all exposed produce in plastic, run the kitchen sponges through the dishwasher (or boil them), and empty the kitchen garbage daily.

From there, the problem is stopping, because you can also clean out that little tray that you forgot was in the bottom of the Keurig, shake the crumbs out of the toaster, soak the oven’s broiler tray in a bucket full of ammonia, wash all the clean plates in the cupboard, re-line the utensil drawer with new shelf paper, and put a thick coating of hand sanitizer on the floor and light it on fire.

Alas, the list of places where thousands more Drosophila could be hurtling from infancy to raw insect sexuality goes on and on. As with any military campaign, progress can be hard to gauge, and flagging morale is a serious problem. How long can a normal person maintain a kitchen that’s as sterile as an operating theater? At some point, the need for order conflicts with another basic need: the need to produce — literally, the need to make food.

A little chaos in a system like a kitchen, or a system like how groups of people talk to one another, or in how we structure a problem in our minds, can be a good thing. Some research suggests that we need a little randomness and chaos in our thinking to jump-start inspiration.

More importantly, trying to work in a kitchen that’s got the bacteria count of a nanotech fabrication facility is going to sap your energy. Keeping track of every stray piece of minced onion or carrot top is not compatible with having an enjoyable time making dinner on a Monday.

Ultimately, the ideal solution to a summer fruit fly invasion is the same solution most of us use for everything else: satisficing. Satisficing means a rational, functional, practical level of performance, as opposed to optimizing. Optimizers want to know that they have made the best choice, come as close as they can to perfection, and expunged every last fruit fly from every corner and crevice of the kitchen.

Satisficers know better. Satisficers say “all things in moderation”. If that means a little wine gets splashed on a counter and breeds a few thousand fruit flies, so be it: apple cider vinegar is cheap.

Fruit flies breed much faster than you can eradicate them, and their growth is exponential. Your best hope is to control their numbers through the hottest part of the summer and remember that, if you live in a temperate zone (assuming that climate change has not rendered that concept meaningless), what to you is a slight chill in the air in September is the End of Days to your home’s fruit fly civilization. Their tiny artists and poets will try to capture the beauty of what it means to be Drosophila — a life made sweet and sad in its mix of brevity and fecundity — but to you and me it is so much random flying around. And, frankly, what can be said but: good riddance?



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Aaron McKeon

Professional planner, unprofessional writer. Member of the American Institute of Certified Planners. Also, a Sunday School teacher.