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How to incubate a parasitic fly under your skin

How to incubate a parasitic fly under your skin


This is the grossest thing you'll see all day

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Entomologists aren't like you and me; they're way more comfortable with truly disgusting stuff. Which is why not one but two entomologists recently announced that they had incubated parasitic bot flies under their skin. On purpose.

Bot flies are "relatively painless unless the larva decides to munch on nerve endings"Bot flies are parasites. First, a female bot fly chases down a mosquito and lay eggs on its belly. Then, when the mosquito gets its next blood meal, the eggs hatch and the tiny larvae drop onto the skin of the animal below, where they burrow in head-first. The bot fly, as a foreign object, inflames the immune system, sending white blood cells to the site — which the larvae use as snacks. Over the course of about 10 weeks, bot fly larvae grow from the size of a grain of sugar to that of a peanut, writes Piotr Naskrecki, one of the bot fly incubators, and an entomologist at the Museum of Comparative Zoology, at Harvard University. This process, as you might expect, is weird for the host, but "relatively painless," Naskrecki writes, "unless the larva decides to munch on nerve endings."

The bot fly is a relatively "friendly" parasite, according to Gil Wizen, the other bot fly host. "It does not transmit any diseases, does not cause any significant damage to the body, does not leave any scars, keeps its area clean from infections by antibiotic secretions and most importantly – unlike other parasites, once it finishes doing its thing, it leaves on its own!" he writes in his account of incubating the larvae. This was his second try; his first didn't go so well for the fly.

Once the fly is big enough, it drops out of its host's skin and forms a pupa. The adult fly emerges, but can only live for a few days, since it has no functioning mouth — and can't feed. Both Naskrecki and Wizen deemed their progeny pretty. "And what a magnificent fly it is!" Wizen writes. "Glowing red eyes, a pointy head with a bright silvery 'face,' and the most dazzling blue abdomen, striking with metallic gloss. For me, this was literally the miracle of birth. No matter how I look at it, this fly is my own flesh and blood." Parents, am I right?

In both cases, the scientists were accidentally infected in Belize — bot flies range from Central through South America. As interesting as the experiment was, Naskrecki writes, he'll make sure he's covered in insect repellent the next time he's in Belize.