Chiggers are not insects but are actually the six-legged larval stage of mites belonging to the family Trombiculidae, making them arachnids more closely related to spiders and ticks. The common misconception is that these tiny mites permanently reside on plants, but the vegetation serves merely as a temporary launch point. Chiggers spend the majority of their life cycle in the soil, and only the microscopic larvae are parasitic to humans and animals. The presence of chiggers on plants is a transient behavior.
Understanding Chigger Habitats
Chiggers are fundamentally ground-dwelling organisms that thrive in specific environmental conditions rather than on a particular species of plant. Their preferred habitat is characterized by damp soil, dense vegetation, and a high degree of shade. They are commonly encountered in overgrown lawns, weedy upland areas, and areas with heavy leaf litter or mulch.
The mites concentrate heavily in transition zones, such as the margins between wooded areas and fields or along ditches and brush thickets. Chigger populations are often spotty, meaning they can be densely concentrated in one small area. The vegetation in these areas, like tall grasses, low-lying brush, and dense ground cover, provides the necessary humidity and shade for the mites to survive.
The adult and nymph stages of the mite life cycle are non-parasitic and live entirely in the soil, where they feed on small arthropods and insect eggs. Adult females deposit their eggs in damp soil or leaf litter. Therefore, the plants themselves are not the source of the infestation but rather a physical structure the larvae use to encounter passing hosts.
The Larval Stage and Questing Behavior
Only the six-legged larval stage is responsible for the itchy bites associated with chiggers. These larvae, which are typically only about 1/150 of an inch in size, seek a host to complete their development. The process by which the larvae position themselves to find a host is known as “questing.”
During questing, the larvae crawl up to the tips of low-lying vegetation, such as a blade of grass, a fallen leaf, or low shrubbery. Once positioned at the highest point they can reach, they wait with their forelegs extended to latch onto any passing host. They are often attracted to the carbon dioxide exhaled by a host.
The larvae require a host to feed for up to three days before dropping off to continue their life cycle in the soil. Chiggers do not burrow into the skin or consume blood; instead, they inject a digestive enzyme that liquefies skin cells, which they then consume. This temporary use of low vegetation is the primary reason people encounter chiggers when walking through overgrown areas.
Preventing Chigger Bites
Avoiding areas known to harbor chiggers, such as unmown fields, overgrown brush, and heavily wooded margins, is the most straightforward method of prevention. When venturing into these habitats, wearing protective clothing provides a physical barrier against the mites. Long-sleeved shirts and long pants should be worn, with the pant legs tucked into socks or boots.
Chemical Protection
Chemical repellents offer a reliable layer of defense against chigger exposure. Insect repellents containing DEET can be applied directly to exposed skin. For extended protection, clothing can be treated with permethrin, an insecticide that kills chiggers upon contact. Permethrin should never be applied directly to the skin but should be allowed to dry completely on clothing.
Post-Exposure Hygiene
After spending time in high-risk areas, immediately taking a warm shower and vigorously scrubbing the skin with soap can help dislodge any chiggers that have not yet attached. Prompt removal of chiggers can significantly reduce the intensity and duration of the subsequent itching.