Chigger mites are of the Trombiculid family which undergo seven stages of their life cycle. The adult chigger does not feed on the host. It is always the larvae and it does not feed on blood. The larvae stage feeds on the lymph and dermis and it is this bite that causes the allergic response of intense itching and the appearance of red dots on your skin. They congregate in groups in grassy areas and subsequently bite in groups. They typically feed on humans for about 3-8 hours. They will migrate to the thinest area of skin as it is easier to get to their meal. This would be anterior legs over the Tibia, over bones of the foot, on genitalia and behind the knees and arm pits.
It should be noted in the United States chiggers do not transmit disease, however, other species can transmit Scrub Typhus. This is very common in China, Japan, Taiwan, South Korea and Thailand.
Bites present as small, red, macular (flattened) or papular(raised) eruptions and are very pruritic (itchy). They are often in groups and clusters and frequently confused with flea bites. This is when the history is very important. Have they been around pets? Have they been camping, hiking etc.? Chiggers do not bury under the skin, however, they are very difficult to see with the naked eye. They are often identifiable with a magnifying lens.