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…