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Tuesday, October 19, 2021

Column: Creepy Crawlies, Part I

On Nov. 2, 1841, a scientist named Berger sent a sealed envelope to the Academy of Science in Paris. When those at the academy opened the envelope, they found documents describing an organism living in the earwax of a man. Berger was the first scientist to describe a parasitic mite called the follicle mite (genus Demodex).

Acarologists (those who study mites) now know that many people have follicle mites. Like all mites, follicle mites are related to spiders and have eight legs. Follicle mites are only 0.2 millimeters long. They burrow headfirst into hair follicles on the face so only their tails stick out. Though the mites particularly enjoy oily faces or faces with lots of make-up, most people will pick up a few mites during their lifetimes.

Feeling itchy yet? Don’t worry – the mites are usually harmless.

“They don’t hurt you and you would never feel them,” said Amanda Hodson, a graduate student in entomology at UC Davis. “They just eat your skin and your sweat.”

That’s comforting.

Follicle mites are the most peaceful of the human parasitic mites, Hodson said. After all, ticks are mites that suck blood and mites called Sarcoptes scabiei cause scabies.

Hodson studies the relationships between worms, mites and insects. Over 45,000 species of mites have been described. Hodson thinks it’s a shame that humans associate mites with disease, not awe.

“The only [mites] we know are the ones we are afraid of,” Hodson said. “Some can be really big and beautiful.”

Mites were around long before humans. We have fossils of mites from nearly 400 million years ago. The 45,000 species we know of are estimated to be only 5 percent of the total number of species.

Mites live in freezing climates, deserts and even deep-sea trenches. Hodson calls the diversity of mites “awe-inspiring.” She pointed out that there’s even a species of mite that lives in honeybee respiratory tubes.

“If you want proof that the universe is complicated, go to mites,” Hodson said.

The thought of mites may make you itchy, but mite populations are helpful in teaching scientists about changing ecosystems. Hodson explained that when you study an ecosystem like a forest, it’s important to track mite populations.

“Species of mites present tells you how healthy your ecosystem is,” Hodson said.

If there are mite species with long life spans, the forest is healthy. If the only mite species are fast to reproduce but have short lives, the forest is in trouble – the environment is only supporting mites that are passing through for a quick meal. A diverse mite population is good.

When I visited Hodson’s lab, she showed me evidence of mite resourcefulness. She had infected an earwig with parasitic worms. The earwig naturally had harmless mites living on it. But once the worms killed the earwig, the tiny mites came out to munch on the buffet of wiggling worms and earwig guts.

Hodson said her work with insects in pistachio orchards has led to an obsession with “things eating other things.” She finds the complex relationships between predators and prey fascinating.

“I think it’s exciting, like an opera,” said Hodson “It’s dramatic.”

Now back to follicle mites.

Hodson had assured me they were harmless, but I needed to know if I had them or not. No one wants to play host to sweat-eating creatures.

I scraped a little skin off my nose, cheeks and eyebrows. I put the skin cells under a microscope slide and – wincing – took a look. Turns out I don’t have follicle mites! (In the areas I checked, at least.)

We all know we live with bacteria partying in our guts, but it’s freaky to think of mites – cousins to spiders – colonizing our faces.

Hodson pointed out mites are amazing because they’ve evolved to exploit every possible resource.

Sometimes evolution grosses me out.

MADELINE McCURRY-SCHMIDT hopes you’ll read Part II next week, where Buster decides to pursue a long-delayed right of passage and then a seal bites off his hand. Just kidding. It’s about bugs. E-mail her at memschmidt@ucdavis.edu.

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