Trombiculidae

Ewing, 1929

chiggers, harvest mites, berry bugs, red bugs, scrub-itch mites, aoutas

Genus Guides

Eutrombicula(Redjigger-mites)

Trombiculidae is a of mites commonly known as (North America) or harvest mites (Britain). The family includes whose larvae are parasitic on vertebrates, including humans, causing skin irritation through a unique feeding mechanism. Only the larval stage is parasitic; nymphs and are free-living . Several species serve as for in East Asia and the South Pacific. The family was formally established by Henry Ellsworth Ewing in 1944, though references to chiggers date back to sixth-century China.

Eutrombicula by (c) 116916927065934112165, some rights reserved (CC BY), uploaded by 116916927065934112165. Used under a CC-BY license.

Trombiculidae by (c) Trevor Van Loon, some rights reserved (CC BY), uploaded by Trevor Van Loon. Used under a CC-BY license.

Pronunciation

How to pronounce Trombiculidae: //trɒmˌbɪkjʊˈlɪdiː//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Larval stage distinguished by six legs, bright red-orange coloration, and microscopic size. The stylostome feeding structure left in skin is diagnostic of exposure. and nymphs show a constricted body not seen in related mite . Distinguished from ticks by smaller size and distinct stages. Distinguished from jiggers (Tunga penetrans, a ) by and feeding mechanism— do not burrow into skin.

Images

Appearance

Nearly microscopic mites measuring approximately 400 μm (1/60 inch) in length. Larvae () are 170–210 μm in diameter, light red in color, and covered in hairs. Nymph and stages show a distinct constriction in the body region. Adults possess eight legs; larvae have six legs. Body has a chrome-orange hue.

Habitat

Forests, grasslands, and vegetation of low, damp areas including berry bushes, orchards, lake and stream margins. Also occurs in drier low-vegetation such as lawns, golf courses, and parks. Larvae congregate on soil clods, matted vegetation, and low bushes. and nymphs inhabit soil, compost, and protected subsurface locations.

Distribution

distribution found throughout the world. Most prevalent in hot, humid regions of Europe and North America. In North America, concentrated in the South and Midwest; scarce or absent in far northern areas, high mountains, and deserts. In Europe, Neotrombicula autumnalis occurs from Western Europe to Eastern Asia. Leptotrombidium deliense occurs in East Asia and South Pacific. Trombicula alfreddugesi is common in southeastern United States, humid Midwest, and Mexico.

Seasonality

Most numerous in early summer when vegetation is heaviest. In temperate regions, females become active in spring when ground temperature regularly exceeds 16°C (60°F). In northern Europe, N. autumnalis active during summer and autumn. In tropical regions, may be continuous year-round. overwinter in protected subsurface locations.

Diet

Larvae: parasitic, feeding on dissolved skin of vertebrate via stylostome. Nymphs and : predatory on small arthropods and their ; also consume plant material.

Host Associations

humans - larval causes trombiculosis (skin irritation)
rabbits - larval
toads - larval
box turtles - larval
quail - larval
small mammals - larval rodents, tree shrews
birds - larval Bonin Greenfinch, Warbling White-, others

Life Cycle

Seven-stage : , prelarva, larva, , deutonymph, tritonymph, and . Only the larval stage is parasitic; all other stages are free-living in soil. Females lay 3–8 eggs per clutch on leaves or among plant roots. Eggs approximately 6 days; prelarvae emerge with three leg pairs and do not feed. After approximately 6 days, prelarvae into six-legged larvae. Larvae attach to for 3–5 days, then drop to ground and develop through nymphal stages (protonymph inactive transitional, deutonymph active with 8 legs, tritonymph inactive transitional) to adulthood. Complete cycle lasts 2–12 months depending on and environment; 1–3 cycles per year in temperate regions, potentially continuous in tropics.

Behavior

Larvae crawl onto from vegetation and attach to feed. They do not burrow into skin but form a stylostome—hardened tube of skin —through which they ingest dissolved tissue. Larvae tend to attach where clothing restricts movement: belt lines, behind knees, sock tops. They detach after 3–5 days of feeding. Post-larval stages are non-parasitic, soil-dwelling, and predatory. and nymphs often found when digging in yards or gardens.

Ecological Role

Larvae function as of vertebrates. Post-larval stages serve as in soil , consuming small arthropods and plant material. Several are significant : Leptotrombidium species transmit Orientia tsutsugamushi, causative agent of , through from parent to offspring.

Human Relevance

Cause of trombiculosis (trombiculiasis, trombiculidiasis)—itchy skin rash with red papules, hives, dermatitis, and . Itching typically develops 24–48 hours after larval detachment. In East Asia and South Pacific, of (Orientia tsutsugamushi), potentially fatal if untreated. Misconceptions about burrowing lead to ineffective home remedies (nail polish, bleach). Treatment involves topical corticosteroids, antihistamines, and hot showers; welts heal in 1–2 weeks. Prevention through protective clothing and prompt washing after exposure.

Similar Taxa

Tunga penetrans (jigger flea)Both cause skin ; jiggers are fleas that burrow into skin, while are mites that do not burrow but form stylostomes. Jiggers remain embedded; chiggers detach after feeding.
Ixodidae (hard ticks)Related arachnid ; ticks are larger, have eight legs in all active stages, feed for days to weeks, and transmit different suites. are smaller, have six-legged larvae only, feed briefly via stylostome, and are nearly microscopic.
Sarcoptidae (scabies mites)Both cause itchy skin conditions; mites burrow into skin to live and reproduce, while larvae feed superficially via stylostome and do not remain in .

Misconceptions

do not burrow into skin or suck blood, contrary to widespread belief. They do not lay in skin . The red welt does not indicate egg-laying. Chiggers are not the same as jiggers (Tunga penetrans). Home remedies attempting to 'suffocate' burrowed mites (nail polish, alcohol, bleach) are ineffective because the mites are not burrowed and have often already detached when itching begins.