Welcome to Chiggers & Redbugs

Common Name:
Chiggers, Redbugs
Scientific Name:


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 ectoparasits of vertebrates including humans. They are found worldwide including the United States. The most common chigger in the Western Hemisphere (New World) is the common chigger, Trombicula alfraddugesi (Oudemans), and this treatment is based primarily on this species as being representative.


Larva very small 1/128" (0.15-0.25 mm) long unengorged to 1/64" (0.6 mm) long when engorged. Body oval, dorsoventrally flattened (top to bottom), not hard- shelled; with 6 legs. Color red to reddish orange. Single dorsal shield or scutum approximately rectangular with 5 hairs (setae), 1 at each corner and 1 midway along front margin, and 2 sensillas (long hairlike structures) with 6-8 branches in outer half. Hairs (setae) 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 (external opening to respiratory system) always associated with coxae I (1 st pair of legs). Adults about 1/32" (0.9-1.1 mm) long; figure-8 shaped. Color bright red, very hairy with velvet appearance.



The developmental stages are egg, deutovum, larva, nymphochrysalis, nymph, imagochrysalis, and adult; larva with 6 legs, nymph and adult with 8 legs. Eggs are usually laid in damp but well drained soil. The deutovum develops within the egg and contains the developing larva. The egg splits open exposing the deutovum from which the larva emerges. They crawl on the soil searching for a suitable host or crawl up grass stems to a height of about 2 3/8-2 3/4" (60-80 mm) and await the passage of a suitable host. The larva attaches to a vertebrate host via its chelicerae, often at the base of a hair. It feeds by partially digesting the host's tissue with its saliva and then ingesting the resulting soup; it does not suck blood or burrow under the skin. After feeding for about 3 days, it drops off the host and burrows into the soil. Here it undergoes considerable tissue resorption and rearrangement as the nymphochrysalis develops. Through a dorsal split in the larval skin and nymphochrysalis, the nymph emerges.

The nymph feeds on the eggs and early instars of other arthropods. After feeding it becomes quiet and develops the imagochrysalis within its cuticle. The adult emerges via a dorsal split in the imagochrysalis and nymphal cuticle. The adult food is the same as that of the nymph. Developmental time (egg to adult) may require 1-12 months depending on conditions of climate, with 1-3 generations per year in temperate regions to 6 generations in subtropical areas. In Missouri the adults overwinter in an earthen cell about 1-1.5" (25-38 mm) below the soil surface, eggs are laid during the first warm spring days, and the adults die shortly thereafter.


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 forests, in mammal nests and burrows, crevices of decaying wood, bat caves, lawns, and marsh areas.

In general the larvae are most abundant in vegetational transition 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 most habitats. The larval activity period varies from 2 months in Minnesota and Massachusetts (July - September) to throughout the year in southern Florida.

When humans are attacked, the larval mites 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 hours 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 any infectious diseases to humans in the United States; in the Orient and other areas of the Pacific, chiggers are vectors of the rickettsiae disease called scrub typhus caused by Rickettsia tsutsugamushi (Hayashi).