chigger

/chig"euhr/, n.

1. Also called harvest mite, redbug. the six-legged larva of a mite of the family Trombiculidae, parasitic on humans and other vertebrates, sucking blood and causing severe itching and acting as a vector of scrub typhus and other infectious diseases.

2. chigoe.

Also, jigger.

[1735-45, Amer.; var. of CHIGOE]

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Larva of some 10,000 mite species, ranging in length from 0.

004 to 0.6 in. (0.1–16 mm). Some are terrestrial; others live in freshwater or salt water. They may be predators, scavengers, or plant feeders, and some are pests of humans, either as parasites or as carriers of disease. In North America, the common chigger that attacks humans is found from the Atlantic coast to the Midwest and Mexico. The larva penetrates clothing and, once attached to the skin, injects a fluid that digests tissue and causes severe itching. After feeding, the larva drops to the ground and begins to mature.

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▪ arachnid

also called  scrub mite,  harvest mite,  bête rouge , or  chigger mite 

      the larva of any of approximately 10,000 species of mites in the invertebrate subclass Acari (the mites and ticks). The name is also erroneously applied to an insect better known as the chigoe, jigger, or jigger flea.

      Chiggers range in length from 0.1 to 16 mm (0.004 to 0.6 inch). The external skeleton is thin and discontinuous. Certain species have eyes, others have none. Spiracles, or breathing pores, when present, are at the base of the first pair of appendages or elsewhere on the front part of the body.

      Some species are terrestrial in habit, while others live in fresh or marine water. Chiggers may be predators, scavengers, parasites, or plant feeders. Various chiggers are pests of man, either as parasites or as carriers of disease. Attacks of chiggers often result in a dermatitis accompanied by intense itching.

      In North America the common chigger that attacks humans is Eutrombicula alfreddugèsi (also called Trombicula irritans). This species occurs from the Atlantic coast to the Midwest and southward to Mexico. The tiny larvae easily penetrate clothing. Once on the skin surface, they attach themselves and inject a fluid that digests tissue and causes severe itching. The surrounding tissue hardens, forming a tube.

      After feeding, the larva drops to the ground and sheds its external skeleton to become a nymph and finally an adult. Nymphs and adults are not parasitic on vertebrates but feed on plant materials and perhaps other arthropods. Eggs are laid singly on the ground or on leaves or stems of low-growing plants.

      Other species of chiggers that were formerly considered to be members of Trombicula but usually are now classified as separate genera include Eutrombicula splendens and E. batatus of North America. In Europe Neotrombicula autumnalis attacks not only humans but also cattle, dogs, horses, and cats. In the East Asia certain species of Leptotrombidium carry the disease known as scrub typhus.

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