National Geographic : 1998 Dec
we know which diseases our parasites carry and how to avoid them; and at least in the more temperate corners of the planet, we don't generally suffer from nightmarish stuff like botflies. Scientists have demonstrated persua sively that our ectoparasites do not transmit the AIDS virus. And though pathogens and parasites can adapt rapidly, our body beasts appear unlikely to cause new plagues in the developed world anytime soon."We have better hygiene, screen windows, air-conditioning,"' says Duane J. Gubler, who heads the division of Vector-Borne Infectious Diseases at the U.S. Centers for Disease Control and Prevention. "Television has made us reclusive, at home at the time when we are at greatest risk of being bitten by mosquitoes." We are spared by being couch potatoes, each of us a lonely and underpop ulated habitat, perched before our television sets, with only our resident bacteria and those low key hangers-on, the fol licle mites, for company. I thought about all this as I looked through the microscope in Cliff Desch's laboratory. I also thought, as so many of us do in moments of aesthetic and personal doubt, about Martha Stewart, who has written "I have always been in spired by nature." I asked Desch what sort of in spiring things the follicle mites might be doing on her forehead and by ex tension on riffraff like me. These mites, he said, aren't much good at crawling to new territo ry. But they spread from person to person when we nuzzle, and because a population thrives in the area around the nipples, they also pass to newborns as naturally as mother's milk. An immigrant mite makes itself at home on a fresh face almost instantly, crawling mouth first into the nearest follicle, with its back to the hair shaft and its stumpy legs to the follicle wall. Since it has no reverse gear, Desch said, it may never come out again. Embedded upside down in our skin, it feeds by using those nee dlelike mouthparts to puncture epithelial cells and suck up the spilled fluids-with no appar ent harm to us. It filters out solids even as small as the mitochondria of the cell, a feat Desch characterized as "near-perfect pre-oral digestion." The mite's digestive process yields so little waste that it doesn't even have an excretory opening. It need never get up to go to the bathroom. The follicle mite is, in truth, a couch potato's couch potato. "And to reproduce?" I asked Desch, with some trepidation, thinking that a mite must get lonely tucked away somewhere out on the vast, windswept expanse of the forehead. The nearest neighboring mite population centers, around the wings of the nose and in the eyelashes, are as distant as oceanic islands. The female, Desch said, may produce a first generation asexually, by parthenogenesis that is, virgin birth. Then she mates with her sons to produce the next generation, up to a maximum population of about ten mites per follicle. ("Oedipus should have plucked out his eyelashes and left his eyes alone," I muttered.) All this passes utterly unnoticed, "the extreme," one biologist remarks, "of an exquisite adapta tion in which each of us is infested right now, but asymptomatically." Some researchers the orize that follicle mites may even benefit us in ways we do not yet understand. In any case, there is nothing, from soaps to systemic med icines, that we can do about it. I left Desch's lab thinking that follicle mites are precisely the ectoparasite we deserve-and that we are lucky to have them, riding on our foreheads, a living reminder that our flesh is merely a part of the natural world. Back home I offered to write my wife an ode to her follicle mites. She handed me a washrag for my forehead and suggested curtly that I keep my infestations to myself. But I knew that in the nature of life on the human habitat, it was already way too late for that.  Join the online forum on body beasts at www.national geographic.com/media/ngm/9812.