Phantom or Real: Chiggers

When I was a little girl, I could still see some, and I absolutely loved the fireworks. We would go as a family to a park in my home town, sit in the grass, and watch that beautiful display of color. I’d go home happy, and in the next couple of days, I’d start itching—the worst kind of itching I’d ever experienced. Little red bites began to appear on me—everywhere that my clothing was tight against my skin. Around my waist, under my shirt, under my socks. It was maddening. Mom put something on the bites to soothe the itch, and I guess it helped some. I just remember how acute that itching was. Mom would say don’t scratch, but it was impossible not to. And, of course, scratching only made them itch worse. The culprit, chiggers (Eutrombicula alfreddugesi).

I haven’t sat in the grass on Owl Acres to find out if we have chiggers, but the chances are reasonably good. They live in the underbrush and the weeds in the fencerows and along the ditches and the edges of surrounding fields.

Bryan had never experienced the particular entertainment of a case of chiggers. He declared them to be a product of my imagination. He said he’d never heard of such a thing. I must have made them up. Just mosquito bites, he’d say. Until now. Now he has the worst case of chiggers I’ve ever seen. He didn’t get them on Owl Acres. He got them on a road trip through Virginia. And he got them worse than anything I’d ever experienced. He had chigger bites under his socks, beneath his underwear, and up to his torso. And my goodness how they itch!

So what are chiggers anyway? They are very real larvae of mites in the genus Eutrombicula. They are also known as harvest mites, red bugs, scrub-itch mites or berry bugs. In spite of the fact that they are bright red, you almost never see them. The larvae that cause all the trouble are less than half a millimeter long. Even the adults are only about a millimeter long. The larvae hang out in the grass and weeds and wait for a whiff of carbon dioxide to tell them that a vertebrate victim is close by. Then they climb up the grass and get on the passing vertebrate. They’ll take cold-blooded vertebrates such as snakes and lizards, but they prefer the warm-blooded type such as birds and people. The larvae have six legs at this point, and short piercing mouthparts. They pierce the top layer of skin and inject their saliva into the spot. This releases some of the host’s cellular fluids, which the larvae gorge on. They don’t actually burrow into the skin like scabies do, and they don’t drink blood like mosquitoes and bedbugs. They just poke that tiny hole, inject that maddening saliva and leave a big red welt that can drive you mad. For some reason, they prefer to leave these welts right where they will be the most irritated by your clothing–around your waistband, under your socks, and worse. They like tight places.

They will spend two or three days gorging on skin cells. When they’ve had enough, they drop off and bury themselves in the dirt. After a week or ten days, they will molt and move on to their next life stage. They leave behind those big welts that can itch for up to two weeks or, in Bryan’s case, three weeks.

After a week to ten days in the soil, the larva emerges as a nymph which developed inside the engorged larvae’s cuticle (outer covering). The nymph now has eight legs and is a free-ranging predator of smaller arthropods. It will change again into a sexually active adult and keep eating smaller arthropods, their eggs, and anything else they can catch. The only stage we’re especially concerned about, though, is the skin-eating larvae. The nymphs and adults are not harmful and help keep populations of smaller arthropods in check by eating them and their eggs.

The adult mites overwinter in the soil and emerge in the spring to mate. I suppose you could call it mating, although they may never actually meet, and there’s no singing, dancing, wooing, or enticing involved in the process. There’s no romance here. The male just wanders around in the grass or dirt, or maybe onto a decaying tree, depositing spermatophores (packets of sperm) along the way. A female comes along and finds a sperm packet. She inserts it into her genital pore, and the deed is done. Two weeks later, she begins laying eggs one at a time. The complete development cycle from egg to adult takes about 65 days on average, and two or three generations may occur in a given year depending on weather and soil conditions.

On the evolutionary tree, mites come closer to spiders than to insects. They’re in the same class as ticks and scorpions and go through the same life stages of egg, larva, nymph and adult. Chiggers are found throughout the United States hiding in tall grass and brushy vegetation. The North American chiggers don’t carry any diseases that could infect a human, although some species in Asia can carry a disease called scrub typhus.

Bryan has finally stopped itching after a full three weeks of misery. And the chances are very good that he now believes in chiggers. There’s a lesson there somewhere!

Photo by Author. Alt text: A few dozens of Bryan’s hundreds of chigger bites decorate his calf, ankle and foot. Even though the chiggers came from Virginia, Bryan is one of the creatures who lives on Owl Acres, so this counts.