sealPurdue News
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July 16, 2001

As chiggers get thicker it's no time to snicker, entomologist says

WEST LAFAYETTE, Ind. – How do you stop a chigger bite from itching?

"Amputation, sometimes," humorist Calvin Trillin once said.

As gardeners head out to pick the fruits of their labors, and families head outdoors for a bit of relaxation, they may encounter the hard, red, infuriatingly itchy bites of the chigger.

But Tim Gibb, extension diagnostic entomologist at Purdue University, says you can prevent chigger bites if you know more about them, and chiggers are interesting creatures in their own right.

Although chiggers are best known as a summer pest, they are actually active from spring through fall. "But it is in the summer months that people are out in their gardens or camping and hiking when they seem to get noticed the most," Gibb says.

This year is normal in terms of chigger populations, but Gibb says that when people call his office to talk about chiggers, they insist he's wrong.

"Anytime someone gets covered with bites, and begins to itch, that year is worst they’ve ever seen," he says. "And whatever month they get them becomes the peak time of the year."

One reason chiggers are thought of as summer pests is that many people are exposed to chiggers while picking fruit, especially raspberries and wild blackberries. "There's just something about blackberry habitats that chiggers love," Gibb says.

Chiggers use the blackberry canes, grass and other plants as diving boards to hop onto a passing meal.

"They crawl up to the highest point on a plant and wait for an animal or person to walk by," Gibb says. "Then they fall onto a person, usually landing on the shoes or lower pantlegs, and then begin crawling up the body looking for a place to bite."

Gibb says people can prevent bites by avoiding walking through tall grasses or shrubs, and staying on paths.

"A lot of chiggers fall on the shoes and pantlegs, so if you’re going to use repellents I’d concentrate on that area," Gibb says. "You should tuck your pants into your socks, and then spray repellent on that area. It’s always best to avoid putting insect repellent on bare skin."

If the bites are severe enough, physicians can prescribe anti-itch creams to ease the suffering.

"Scratching the bite can cause it to become infected," Gibb says. "Just keep it clean, and avoid scratching it, and in a couple of days it’ll go away. In the meantime, enjoy the blackberry cobbler – it may keep your mind off the itching."

Here are a few facts about chiggers that you can share with your family as you sit scratching, which might annoy them enough to help them momentarily forget about their own itch:

• Chiggers aren't insects, but arachnids, just like spiders and scorpions. They are a type of mite related to ticks. "Chiggers is a common name we give to the larvae of several species of mite," Gibb says.

• Sometimes tiny red mites are seen, especially on light-colored concrete. These are adult chiggers, which don't bite people, but instead feed on insect eggs and other insects. The chigger larvae are much smaller than the adults– half a dozen of them could fit on the period at the end of this sentence. Chigger larvae can scarcely be been seen without a magnifying glass.

• Although adult chiggers have eight legs, when they are in their biting larval stage they have just six. And unlike ticks, chiggers don't carry Lyme disease or Rocky Mountain spotted fever.

• Chiggers aren't really good at biting, and can bite only thin skin, which is why they bite children or women more than men. They like to bite in soft, light and moist areas of the body where the sun and weather haven't made the skin tough and dry. These are places where chiggers are least welcome.

• Chiggers don't burrow into the skin. Instead they pierce a skin cell with their mouths. Their saliva contains an enzyme that causes the skin cell wall to liquefy. The body's immune system reacts to the foreign enzyme resulting in a hard, red wall at the spot of the bite. The chigger capitalizes on this – it uses this round wall, which is called a stylostome, as a straw. After the chigger has had its fluid meal, it drops off.

• In medical terms, these hard, red welts are called papules. A bite will begin itching three to six hours after a chigger has bitten the skin. "At that time, the chigger is long gone," Gibb says. "By the time you begin to itch, it's too late to prevent the chigger from biting."

The bite will develop a red circle, or welt, within 10 to 16 hours, and will continue to itch for up to two days or more, depending on the individual's reaction. For someone with dozens of bites, this is truly an unpleasant experience.

"If you absolutely must call in sick to work because of chigger bites, tell the boss that you have been diagnosed with arachnid papules," Gibb suggests, tongue-in-cheek. "That is going to sound much worse than saying you have a bunch of chigger bites."

• Because chiggers cannot hold on well, they are easy to remove. Taking a shower with plenty of sudsy soap will remove them. "They don’t hang on people very well because we don’t have fur. To keep from falling off, they have to get in areas where clothing fits tight, like the tops of socks, the groin area, at the waistband, or in the armpits where shirt sleeves fit tightly," Gibb says.

"So if you want to avoid chigger bites while picking raspberries, doing it naked may help," he jokes.

• People often see a red dot in the middle of a chigger bite, and assume that the chigger has burrowed into the skin. However, that red dot is actually the stylostome. "There are mites, such as the scabies mite, that burrow into the skin, but the chigger doesn't," Gibb says. "People sometimes resort to strange chigger remedies such as coating their bites with Vaseline or nail polish in an effort to suffocate the chigger. In fact, by the time the bite begins itching, the chigger has long since dropped off. You can't kill something that’s not there. The itch is simply our bodies' reaction to the bite."

• Sometimes the bite forms a white cap, which is the top of the stylostome. Scratching this cap off often causes a drop or two of the liquid inside the bite to ooze out. Scratching the cap off also can result in an infection.

• Chiggers tend to localize in small areas, which means that after a picnic, one person can be covered with bites and another, who was in a different spot, may hardly have any bites at all.

Finally, although the word chigger sounds funny and is easy to rhyme, Purdue's Tom Turpin, an entomologist and humorist who teaches a course on insects and literature, says to his knowledge, no one has yet penned a poem about the chigger.

He says, however, there is one little limerick written years ago by entomologist H.B. Hungerford:

The thing called a chigger,
is really no bigger,
than the smaller end of a pin,
but the bump that it raises,
just itches like blazes,
and that's where the rub sets in.

For more information about chiggers, the Purdue Extension publication, "Chiggers and Their Control," is available online, or at Purdue Cooperative Extension county offices throughout Indiana.

Sources: Tim Gibb, (765) 494-4570; tim_gibb@entm.purdue.edu

Tom Turpin, (765) 494-4568; tom_turpin@entm.purdue.edu

Writer: Steve Tally, (765) 494-9809; tally@aes.purdue.edu

Purdue Ag Communications: (765) 494-2722; Beth Forbes, Ag News Coordinator, bforbes@aes.purdue.edu; http://persephone.agcom.purdue.edu/AgCom/news/

Purdue News Service: (765) 494-2096; purduenews@purdue.edu


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