Chigger
Introduction
The common name of redbug probably comes from the usual bright red
color of the larvae, which attack humans; in Europe they are called
harvest mites because of their abundance in the autumn which is field
crop harvest time. Only the larval stage is a pest, being an
ectoparasite of vertebrates including humans. They are found worldwide
including the United States. The most common chigger in the Western
Hemisphere is the common chigger, and this treatment is based
primarily on this species as being representative.
Recognition
Larva very small 1/128" long to 1/64" long. Body oval, dorsoventrally
flattened, not hardshelled; with 6 legs. Color red to reddish orange.
Single dorsal shield or suctum approximately rectangular with 5 hairs,
at each corner and 1 midway along front margin, and 2 sensillae with
6-8 branches in outer half. Hairs of body giving a hairy appearance;
22 on dorsum, 14 on venter. Palpal thumb-claw process distinct. Seta
on palpal coxa posterior to palpal femur. Uristigmate always
associated with coxae1.
Adults about 1/32" long; very hairy with velvet appearance.
Habits
Only the larva is parasitic, and on a wide range of vertebrate hosts
including mammals, birds, reptiles, and amphibians. The nymphs and
adults are free-living predators. Adults live in the soil of
grasslands and forest, in mammal nest and burrows, crevices of
decaying wood, bat caves, lawns, and marsh areas.
In general the larvae are most abundant in vegetational transpiration
zones such as the junction of forest and grass, along margins of
swamps, blackberry patches, and brush thickets. In areas such as Ohio,
they are found in lawns and in Kansas they have been collected in host
habitats. The larval activity period varies from 2 months in Minnesota
and Massachusetts to throughout the year in southern Florida.
When humans are attacked, the lrvalmites most frequently attach
themselves at hair follicles in areas where clothing is tight fitting
such as the ankles, waist, and armpits. Itching is usually not felt
for 3-6 hrs after attachment and may persist for up to 2 weeks.
Scratching often removes the offending mite but can result in
secondary infection. Chiggers are not known to transmit infectious
diseases to humans in the United States; in the Orient and other areas
of the Pacific, chiggers are vectors of the rickettsial disease called
scrub typhus caused by Rickettsie tsutsugamusk.
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