Chigger (Trombiculidae): biology, bites, habitat, and prevention

Appearance and feeding

Individual chiggers are tiny—often far smaller than 1 millimetre—and can be difficult to see without magnification. Their colour ranges from bright red to orange or brown. Larvae attach to the host's skin with mouthparts that pierce the outer layers and inject digestive enzymes, creating a feeding tube called a stylostome. This process causes a red welt and intense pruritus rather than a true burrow; the mite does not live under the skin. Bites commonly appear a few hours after exposure and the resulting irritation can last days to weeks.

Life cycle and ecology

Trombiculid mites have a multi-stage life cycle: egg, larva (the only parasitic stage), nymph, and adult. Larvae quest for hosts on vegetation and are most abundant where tall grass, weeds or low vegetation provide humid microclimates. Typical habitats include forests and woodlands, low-lying damp areas near lakes and streams, berry patches and orchards, but chiggers can also be found in lawns, parks, golf courses and other drier sites when conditions are suitable. Populations usually peak in late spring and early summer when vegetation is dense.

• Tall grass and undergrowth provide favoured ambush sites for larvae.
• Trombiculidae is the family name that groups chigger species.
• Several species within the family include those that bite people.
• Larvae are the only stage that feed on vertebrate hosts; see larval behaviour for details.

Common regional examples include Trombicula alfreddugesi in parts of North America and Trombicula autumnalis, the "harvest mite", across Europe and into Asia. Other localities and species are documented in field guides and regional faunal lists.

Symptoms, treatment and significance

Bites typically produce intensely itchy papules or wheals and can be confluent in areas where clothing is tight or the mite aggregates (under knees, around the waist, armpits, groin). Secondary skin infection may follow excessive scratching. First-line care includes thorough washing with soap and water, cool compresses, topical anti-itch preparations such as calamine or hydrocortisone, and oral antihistamines when needed. Persistent or infected lesions warrant medical assessment.

1. Intense irritation and scratching are the common complaints after exposure.
2. Unlike ticks, chiggers do not transmit many common human diseases, but some species of trombiculid mites in Asia are vectors of scrub typhus (Orientia tsutsugamushi) and are of public-health importance.
3. Check clothing and pets; wash garments in hot water to remove attached larvae (woodlands, berry bushes, orchards are frequent exposure sites).

Prevention and distinguishing facts

Prevention focuses on reducing skin exposure and avoiding infested habitat. Practical measures include wearing long sleeves and high socks, tucking trouser legs into socks, using insect repellents on skin and clothing, and treating outdoor gear with permethrin. After visiting likely areas, showering and laundering clothes promptly helps remove larvae. Chigger bites are often mistaken for flea or mosquito bites, but chigger lesions are characteristically very itchy and often cluster where clothing is tight.

• Chiggers occur in both damp and some drier environments such as lawns, golf courses and parks.
• They are most numerous when weeds and grasses are heaviest.
• In North America and Mexico see regional species accounts; in Europe consult faunal guides that cover the range from Western Europe to Eastern Asia (regional distribution).

For more detailed identification and local guidance, consult regional entomology resources or public health websites. If bites are severe, spreading, or show signs of infection, seek medical attention.