Fruit flies, the simple little things that buzz around the fruit you swore you'd eat and the jack-o-lantern you swore you'd throw out, can diagnose themselves with intestinal parasites — and drink alcohol until they're all better again.
Fruit flies really seem to have a bad time of it. They get constantly experimented on in labs, sprayed with every poison known to man, encouraged to mutate, or exposed to radiation. They get swatted and eaten in the wild. And even when nothing goes wrong, a rich, full life for the drosophila melanogaster consists of one month of eating discarded fruit.
That month will be cut horribly short if a wasp gets to them. Wasps will lay their eggs inside a fly, or in a fly larvae. Those eggs will hatch, and the wasp larvae will eat the fly from the inside out. But the flies have found a way to prevent their fate. It turns out that wasp larvae, being used to being laid in any hapless insect that a wasp comes across, are cheap drunks. Fruit flies, however, have spent generations eating whatever fruit is lying out in the sun. Fruit lying out in the sun ferments, so fruit flies have a massive amount of alcohol in their diet. This alcohol is not good for wasp larvae. But it's not a coincidence of diet that cures the fruit flies. Flies infected with the parasite will literally fly around looking for some ethanol, and then gulp down as much of it as they can. Eventually, they'll kill off the larvae within, and find some other food. The flies can instinctively self-diagnose and drink themselves healthy again.
Image: Wiki Commons
Via Current Biology.