Where do fruit flies come from? One day, my apartment was a shining beacon of hope, and one 60-hour workweek later, there was a spontaneous swarm. How do they all appear from nowhere so quickly?
Suspiciously With Fruit
Put down the piece of fruit you might have in your hand. Science has something to tell you, something you might find a bit disturbing. The flies were in the fruit from the start. Somewhere far away—perhaps Florida, Texas, the Central Valley of California, a dense plantation in South America, or a farm in China—a female fruit fly placed a fertilized egg beneath the skin of the piece of fruit sitting in your kitchen, perhaps in your hand right now. In the long journey to your kitchen, the eggs hatched in the fruit. After your miserable workweek—with the fruit languishing in a basket, uneaten—the larvae had a chance to mature enough to become flies, fuck like mad in your kitchen, and continue their glorious life cycle.
Science happens to love fruit flies and congratulates you on your mighty crop. Fruit flies are actually one of two different families of flies that have independently evolved toward the same niche: Drosophila and Tephritidae. Both are somewhat awesome—scientifically speaking.
Drosophila (particularly the stylish Drosophila melanogaster) helped us unravel the most basic aspects of genetics and DNA. Beyond being prolific and easy to grow (as you've figured out), Drosophila have only four chromosomes. In their salivary glands, these four chromosomes undergo a funky mega copying—resulting in chromosomes easily seen with plain old microscopes. By studying Drosophila, scientists were able to figure out how DNA in chromosomes ends up being controlled, different patterns of inheritance of genes, and even how a single fertilized egg cell can make an entire complex organism. Right now, as you read this, scientists the world over are busy opening up FlyNap, taking out their paint brushes, and slowly sorting out mutated flies to better understand how we (humans) are put together. (Pro tip from someone who worked next to a fruit-fly lab: Wet hands capture and smash fruit flies better than dry hands. Also, a cone over a jar filled with something sweet acts as an excellent fruit-fly trap.)
Tephritidae are a bit more annoying—the destroying-entire-crops sort of annoying. Still, scientists found some fun with them. By sterilizing male Tephritidae (usually by irradiation) and spreading these dud males over crop fields, infestations of these sorts of fruit flies can be kept in check. The dud males compete with fertile males, messing up the reproductive cycle of the fly. It's a simple, pesticide-free means of keeping bananas in your kitchen. This same trick—make dud males in the lab to reduce the number of a pest insect—is now being considered against mosquitoes as a way of defending against malaria.
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