Got Chiggers? It Figures!

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Published on: Jun. 2, 2000

Last revision: Nov. 5, 2010

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.

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