Got Chiggers? It Figures!

By Tom Cwynar | June 2, 2000
From Missouri Conservationist: Jun 2000

How many have suffered from chiggers? Probably nearly everyone in Missouri, at one time or another. That's because chiggers are ubiquitous in the state. That means they are everywhere, from north to south, east to west, corner to corner. They inhabit woodlots, lawns, fields, golf courses and parks. They hang out in wet areas and in dry pastures. You'll find them in berry patches, on stream banks and in flower gardens; and if you linger too long in a clump of them, they'll inhabit you, too, from toenail to cowlick or ponytail.

Chigger mites are bright red members of the genus Eutrombicula. We have at least two species - Eutrombicula alfreddugesi and Eutrombicula splendens - and possibly four different species of chiggers in Missouri. However, all are closely related, and the species have similar life cycles.

In the adult stage, chiggers are sometimes called red bugs or harvest mites. Adult chigger mites have eight legs and are a little larger than the period at the end of this sentence. You can sometimes spot them in the soil, but they are harmless to us. They feed on insects and their eggs - even mosquito eggs - as well as on smaller mites.

Chigger adults bear problem children, however. At least their children are a problem for humans. For most of the period from spring through fall, adult female chiggers lay eggs almost daily. Tiny larvae, orange-yellow to light-red and about 1/5th the size of a period, hatch out about a week later. The six-legged larvae, too small for most people to see with the naked eye, create distress all out of proportion to their size.

To mature, chigger larvae must feed on animal tissue. This is the only stage in the chigger mite's life cycle in which it is parasitic.

Larvae improve their chances of encountering an animal host to parasitize by climbing to the tops of grass blades, twigs and other objects in their environment and waiting. They are sensitive to movement and, some say, to the carbon dioxide animals exhale. Whenever a potential host comes within reach, they nimbly hitch a ride.

Once aboard, chiggers roam around, seeking possible attachment sites. They move relatively slowly and, at least on humans, their travel can be impeded by folds of flesh or barriers, such as elastic leg holes or waistbands of shorts, watchbands, backpack straps and sock tops. These sites tend to accumulate chiggers like fence lines attract cattle.

Places where clothing fits snugly also offer chigger larvae the advantage of something to press against to attach themselves. Imagine a little chigger pushing its back or legs against the elastic of your shorts to help it pierce your skin. Imagine also how many points of leverage might be provided for hungry larvae by a single pair of support hose.

Chigger larvae also push against opposing flesh, which helps explain why bites tend to occur more frequently in the underarms, between the thighs, at the backs of knees and in elbow crooks. Chiggers also find it easier to attach where skin is thinner, not leathered by exposure. Some of these sensitive areas are difficult to scratch in public.

Most chigger larvae feed at the site of a hair follicle or pore. Chiggers don't sting like bees or suck blood like mosquitos or ticks, rather they scrape or puncture the skin with bladelike mouthparts, called chelicerae. Once a chigger has an opening, it injects saliva, which contains proteolytic enzymes, to liquify the tissue so it can ingest it.

Our immune system walls off the area where the chigger has injected its saliva, forming a narrow, hardened tube, called a stylostome, through which the chigger feeds, as if through a straw. If nothing interrupts its meal, it will feed for three to four days before dropping off.

Chiggers don't burrow into the skin. Some swelling may slightly envelop a chigger, but the chigger remains on the outside, and all it takes is a slight scratching to remove it. A scratched off chigger will not bite again.

Because most of us respond to chigger saliva with itching and scratching, we do not make good hosts for the larvae. They more successfully feed on reptiles, including lizards, snakes and turtles, or birds or small mammals. But, too hungry or opportunistic or not schooled enough to be fastidious, chigger larvae will attempt to nourish themselves on human flesh.

After tromping around outdoors, you may be able to feel chiggers crawling over your skin or attempting to attach themselves. That's a subtle warning to take action to remove them. Many more chiggers roam over us than ever bite. Chiggers usually come in droves, so it's possible to have dozens, hundreds or even thousands on our bodies at one time.

Our normal movements and hygiene, along with the difficulty the larvae have gaining a mouthhold on us, keep most chiggers from successfully attaching, but people have reported hundreds of bites resulting from a relatively short exposure to chiggers.

Unlike ticks, to which they are related, chiggers are fragile. A shower or bath following exposure to chiggers will remove most of them. If a bath isn't available, a brisk toweling down should dislodge or crush most of them. And you better change your bedding, if you've suddenly ran to the shower after feeling infested during the night.

Avoiding chiggers is difficult because you can't see them. In Missouri, chiggers bustle about from April to October. During the summer, peak activity times are around dawn and dusk and during mid-morning, as the temperature rises into the high 70s and low 80s-their apparent preferred range-and before the sun has had a chance to burn off the evening dew.

Chiggers need both moisture and shade. They tend to be more abundant during rainy spells. During the heat of the afternoon or during long dry spells, they may retreat into the soil. Overcast or humid days seem to draw them out en masse.

The worst places for chiggers are where grass or weeds grow tall enough or thick enough to shade sunlight from the soil. Lake shorelines, river banks and wood edges are notorious chigger haunts.

Chigger larvae tend to occur in clumps, what you might call "mite islands." One spot in a field may be full of chiggers, but a similar spot nearby may not have any. Do you feel lucky?

Any contact with vegetation has the potential to allow chiggers to climb onto you. When you sit or recline on the grass, you make it easier for chiggers by letting them climb aboard at several body terminals. Brushing against trailside branches or weeds or leaning into brush to pick berries invites a chigger infestation.

You can identify chigger hotspots on your lawn by placing a 6-inch square of black cardboard on edge in the grass. Return a bit later and examine the upper edge with a hand lens. If chiggers are present, they will crawl to the top of the piece, where their minute reddish or orangish bodies will be visible against the black edge. Observers also have reported spotting chigger larvae against the background of their polished black shoes.

Chiggers can infiltrate the weave of most fabrics, but you can reduce the numbers that reach your skin by wearing long-sleeve shirts and long pants with the cuffs tucked into your socks. Those extremely sensitive to chigger bites should pretreat their clothes with a commercial aerosol containing the pesticide permethrin.

Ridding Your Yard of Chiggers

Can I burn them away?

Over the eons, chiggers have become well-adapted to Missouri's frequent fires. They survive a burn by burrowing into the soil.

Can I kill them with chemicals?

Chiggers represent only a small number of the myriad tiny creatures that inhabit your lawn or yard. The majority of these insects and animals do no harm to us and some of them are beneficial. Broad-based insecticides, such as Sevin (TM), may create a sterile environment if reapplied often. However, any chemical treatment poses some risk to children, pets and other animals, such as deer and birds.

What can I do?

Chiggers need shade and moisture. Close cropped lawns are, at best, a marginal habitat for them. They much prefer brush and long grass or weeds. If you care for your yard diligently, over time you will have fewer and fewer chiggers in your lawn

If you are sensitive to chiggers, apply a permethrin-based aerosol insecticide to clothes that you wear outdoors.

Insect repellent containing DEET also works. If you don't like to put insect repellent on your skin, spray it on your clothes and shoes, instead. Before these chemicals became available, people relied on dusting sulfur, kerosene or oil of citronella to ward off chiggers.

Chiggers don't carry any diseases that affect us. However, bites can itch so much that we face the threat of secondary infection when we scratch them with a dirty fingernail. When the itching becomes intense, we may be tempted to use a rusty wire brush, if one happens to be within reach.

Scratching, however, is a no-no; in addition to increasing the chance of infection, it keeps a bite open and prevents it from healing. In some people, chigger bites may cause a more general, hivelike reaction that may require treatment by a physician.

A chigger bite usually shows up as just a small, pimplelike reddened bump. By the time you are aware of this welt or bump and feel the itching, which tends to intensify for a day or more, it is too late to do much about it. In fact, it's likely you've already scratched off the chigger that bit you.

A rule of thumb is that the poignancy and duration of the itch is directly proportional to the amount of time a chigger remains attached to you. Remove the chigger right away, and you likely will experience minimal discomfort. If, on the other hand, you sleep with chiggers and they have all night to feed before you wake up scratching, you may itch for another two weeks.

As a chigger bite heals, the top of the hardened tube, or stylostome, is usually visible. If you scratch off its dried cap, liquid oozes out.

Most remedies for chigger bites attempt to remedy the intense itching, which seems to get worse before it gets better. Over-the-counter medications often contain antihistamines, such as hydrocortisone. Others contain analgesics and anesthetics.

An important property of any remedy is to seal the wound from air. That's why some home treatments involve applying nail polish or roll-on deodorant. One reader said he used an anti-hemorrhoidal cream; another suggested meat tenderizer. Calamine, Vaseline, cold cream and baby oil also keep air from the site and may be effective.

Much more complicated home remedies have been developed to ease the itch of chigger bites and hurry the healing process. Most of these contain benzocaine, alcohol, salicylic acid, methyl salicylate and water. Purchasing some of these ingredients may require a doctor's prescription.

Time is probably the best healer for chigger bites. Of course you'll pass that time in a miserable state, fussing, gritting your teeth, tossing your bedclothes and moaning feebly to family, friends and inanimate objects.

On the positive side . . .

OK, let's not get silly. We can probably all agree that when it comes to chiggers there is no positive side

This Issue's Staff

Editor - Tom Cwynar
Managing Editor - Jim Auckley
Art Editor - Dickson Stauffer
Designer - Tracy Ritter
Artist - Dave Besenger
Artist - Mark Raithel
Photographer - Jim Rathert
Photographer - Cliff White
Staff Writer - Jim Low
Staff Writer - Joan McKee
Composition - Libby Bode Block
Circulation - Bertha Bainer