For Fruit Flies, Alcohol Really Is Mommy's Little Helper

Feb 22, 2013
Originally published on February 25, 2013 12:26 pm

Many a mom has reached for a glass of wine after a long day of tending children. But only fruit fly moms use their version of Chardonnay to guard their babies from harm.

When fly moms see marauding wasps, they seek out the alcohol in fermenting fruit, and lay their eggs there, according to new research. The alcohol is toxic to the wasps, but not to the fruit flies. They've evolved a tolerance for hooch.

No only do the fruit flies babyproof with alcohol, when given a choice they'll pick just the right proof — about 3 percent. That's considerably less than the 12 to 14 percent in a glass of wine, but evidently enough to do in those lightweight wasps.

This news comes from Todd Schlenke, an evolutionary geneticist at Emory University who is making a bit of a specialty of studying the relationship between fruit flies and booze. His study was published in the journal Science.

A year ago, he reported that fruit-fly larvae will self-medicate with alcohol if they've been attacked by a wasp. The wasps lay eggs in the flies, and the alcohol kills the wasp larvae, saving the fly's life.

But some wasps are learning how to hold their liquor, Schlenke says, and the fruit flies may need to turn to more potent drink or figure out another survival strategy.

"It's sort of an arms race, I think," Schlenke says. "The flies do something to avoid being infected, and the wasps learn how to get around it."

Anthropomorphizing can be slippery, but it's hard not to feel a certain sympathy for these lowly fruit flies, whose drinking habits seem to echo ours in so many ways. For instance, it looks like fruit flies also turn to the bottle to nurse heartache. When a male fruit fly fails to mate with a female, he'll be more likely to start slugging down ethanol than the guy who scored, according to a study last year.

So why spend so much time hanging out with these "bar" flies? Schlenke studies the tiny flies to learn about big things like memory, heredity, and evolution.

For example, the mother fruit fly's ability to spot dangerous wasps is so refined that she'll only head for liquor when they see a female parasitic wasp (the males pose no threat to the young). "They only have to see the wasp once, and they remember," Schlenke says.

And even though the fruit flies have been living in the laboratory for many, many generations, they have no problem recognizing the danger posed by a wasp the moment they see it.

Ah, science!

Schlenke's revelations on the drinking habits of fruit flies have not only landed him in prestigious journals like Science, they've earned him a hat-tip from the satirical newspaper The Onion, which quipped, "I'm sure at least some of those flies also drink because of their crippling depression."

"Honestly, I think maybe The Onion is the highlight of my career," Schlenke told The Salt.

We bet the fruit flies will drink to that.

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