How do chiggers bite humans?
Chigger mites infest human skin via areas of contact with vegetation, such as pant cuffs or shirt sleeves and collars. They migrate on the skin in search of an optimal feeding area. A common myth about chiggers is that they burrow into and remain inside the skin. This is not true. Chiggers insert their feeding structures into the skin and inject enzymes that cause destruction of host tissue. Hardening of the surrounding skin results in the formation of a feeding tube called a stylostome. Chigger larvae then feed upon the destroyed tissue. If they are not disturbed (which is rarely the case because of they cause substantial itching) they may feed through the stylostome for a few days.
The chigger's mouth and feeding structures are delicate and are best able to penetrate the skin at areas of wrinkles, folds, or other areas of skin that are thin. Most bites occur around the ankles, the crotch and groin areas, behind the knees, and in the armpits. Barriers to migration on the skin such as belts may be one reason that chigger bites also commonly occur at the waist or at other areas where their migration is prevented by compression from clothing.