The end of fall is bittersweet for those who enjoy observing the last of the season’s invertebrates, amphibians, and reptiles. For these cold-blooded animals, winter’s low temperatures make it difficult to remain active. They will seek hideaways under stones, logs, leaf litter, or old burrows and wait out winter hidden away, ready to continue their life cycle when spring arrives. The beginning of the cold season also marks a reprieve from unwanted encounters with certain tiny immature mites: chiggers.
The period from May until frost is regarded as chigger season. The term “chigger” is used to name the types of mites in the family Trombiculidae that are parasitic during their larval stage. Several chigger species occur in Texas, but two tend to be content with humans as hosts: Eutrombicula alfreddugesi and Eutrombicula splendens. They prefer to inhabit prairies or along the edges of wooded areas. Even within favorable habitats, however, the distribution of chiggers is often spotty — they may be concentrated heavily in one spot while absent nearby. To a hiker, it becomes hard to detect when and where these chiggers may grab onto shoes or clothing before selecting a place to feed.
Contrary to popular belief, chiggers do not burrow into the skin but pierce the surface with their mouthparts and inject digestive enzymes that break down the tissue to consume. It is having a “you” protein shake before molting to its next life stage. This fluid, injected into the skin, causes the itchy reaction in most humans; it has a two-fold effect, initially liquifying the cells, then secondarily hardening them to form a straw-like feeding tube, stylostome, through which the chigger can continue to feed. Then the after-effects are most noticeable and memorable. This parasitic digestion makes our skin intensely itchy within hours, and bright red welts may begin to appear.
The chigger has to find a tender area to attach to and often needs something against which to push its legs to force its mouthparts into the skin — hence their preference for the edges of socks, elastic bands of underwear, waistbands, and cuffs. The tight clothing gives them something to push against while they attach.
Winter is a seasonal repose for chiggers that feed on various hosts, including small mammals, birds, reptiles, amphibians, and, given the opportunity, US! They will spend the winter in the soil, evading the cold weather until spring arrives. Chiggers may be considered unbeneficial, but they are an important part of the ecosystem. During most of their life stages, they prey on soil invertebrates. Though these immature mites may be an unintended consequence of hiking, there are a couple of techniques to mitigate their encounter: wearing protective clothing such as long pants and closed-toed shoes, tucking pants legs inside boots, and using insect repellent. The colder weather may delay us from observing cold-blooded creatures, but it also serves as a natural reprieve from these too-close chigger encounters.