Chiggers

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Chiggers, sometimes called the “redbug” or “harvest mite,” are the larval stage of a mite (Trombicula alfreddugesi) and technically they are not insects. Chiggers are "arachnids," in the same family as spiders and ticks. During summer, chigger larvae climb onto people and animals while they walk around in infested outdoors vegetation. Chiggers are parasites and their feeding leaves intensely itchy, small reddish welts on the skin.

HOW DO I KNOW IF I HAVE CHIGGERS?

  • Chiggers are nearly impossible to see without the aid of a magnifying glass; but the itching that follows a chigger bite is hard to miss.

  • Chigger bites often develop tiny red bumps that look like blisters, tiny hives, or small pimples.

  • People are often bitten by chiggers around the ankles, waist, under arms, and in skin folds after they have been in an outdoor area infested with chigger mites.

WHY DO CHIGGERS BITE?

  • The chigger larvae must feed on animal tissue in order to mature. The chigger mite is only parasitic during the larvae stage of its lifecycle.

  • Larvae wait in large numbers on the tops of grass, leaves, and twigs – usually less than a foot off the ground – for a warm-blooded animal to brush past. They are attracted to the carbon dioxide exhaled by the host and are sensitive to movement. Typically, dozens or more chigger larvae will fasten onto a host at one time.

  • Once on the host, the chigger larvae look for possible feeding sites. Often chiggers will stop to feed where their movement has been impeded by tight clothing such as a waistband, sock top, or even a backpack strap. The back of knees, under arms, between thighs, in the crook of elbows, and other areas where the skin is folded or thin are also prime feeding areas for the chigger larvae.

  • To feed, the chigger inserts its mouthparts, called chelicerae, into the host’s skin; usually in a skin pore or hair follicle. Once the chigger is attached, it secretes saliva, which contains proteolytic enzymes, into the host’s skin. The digestive enzymes liquefy the skin tissue so the chigger can ingest it.

  • The area around the chigger bites soon hardens and a feeding tube, called a sylostome, forms in the puncture wound. It is the feeding tube that causes the itchy, red bump.

ARE CHIGGER BITES DANGEROUS?

  • Not in North America*. While chigger bites can cause intense itching and may cause an allergic reaction in some people, chiggers in our area are not known to transmit any disease-causing pathogens.

  • The itching from chigger bites can usually be treated with over-the-counter ointments. The bumps will heal within two weeks.

  • Secondary infections from scratching are possible.

(* Another species of the mite, Leptotrombidium delicense, found in East Asia and the South Pacific can carry the tiny bacterium that causes scrub typhus.)

HOW DO I GET CHIGGERS OFF ME?

  • Chigger larvae are fragile creatures.

  • Take a hot shower or bath soon after you have been in an area prone to chiggers. Apply a thick lather of soap, rinse, and repeat.

  • A brusque toweling should dislodge or crush any remaining larvae. (Even without a bath.)

WHAT DO CHIGGERS LOOK LIKE?

  • Adult mites are approximately 1/60” in length, have eight legs, and are reddish-orange in color.

  • Nymphs are yellowish and have eight legs.

  • Larvae have six legs, are yellow to light red in color, and have a body diameter of approximately 1/125” - 1/100”. 

WHY ARE CHIGGERS IN MY YARD?

  • Chiggers most likely hitched a ride into your yard while feeding on reptiles, amphibians, or small mammals. 

  • Your yard will be attractive to chiggers if there is tall grass, weeds, or shrubbery and moisture to survive. 

  • Also, plenty of organic material on or in the soil provides a suitable environment for the adult mites.

WHAT DO CHIGGERS EAT?

  • Unlike mosquitoes, ticks, or bed bugs that feed on blood, chigger larvae feed on liquefied skin tissue.

  • Nymphs and adult chiggers feed on decaying organic matter and insects in the soil. They are not considered a pest to humans.

WHAT IS THE LIFECYCLE OF CHIGGERS?

  • Chiggers go through a complete metamorphosis life cycle and contain four separate and distinct stages: egg, larva, nymph, and adult.
  • In the spring, Adult female mites lay from one to five eggs per day in leaf litter, vegetation and lawns. After five to seven days, the eggs hatch into 6-legged chigger larvae.
  • Chigger larvae will feed on the skin tissue of a warm-blooded host for 3-4 days and then drop off the host to molt.
  • After a week or ten days in the ground, the larvae molt into a nymph with eight legs.
  • After two weeks to one month, nymphs molt into adults. An adult chigger mite resembles the nymph, but is larger. 
  • Chigger mites are active when the ground temperature is between 77°F and 86°F.
  • Adult chiggers overwinter in protected places. They will die if exposed to temperatures colder than 42°F.
  • In total, the life cycle of the North American chiggers require 50 to 70 days to develop from egg to adult.
  • In Minnesota there is only one generation per year.

5 INTERESTING FACTS ABOUT CHIGGERS:

  • Chiggers typically will not survive on humans more than three days.

  • Chigger larvae attach to a host, but they do not burrow into the flesh.

  • The itching from a chigger bite does not begin until three or more hours after the feeding.

  • It is possible to have hundreds or even thousands of chiggers on your body after being in an infested area. Fortunately, chigger larvae cannot easily attach, so relatively few chiggers successfully bite.

  • Chiggers live in every country around the world.