Chiggers
Order: Acari
Family: Trombiculidae
Scientific Name: Trombicula
What’s itching you this spring? One of the common complaints of the spring is the entomophobic situations that arise. Some “itch” or “bite” problems can be attributed to pests, but usually not indoor ones. Chiggers can cause itching problems on people who have gone outside during their lunch hour or picnicked over the weekend, and return home or to work itching. These mites infest humans during only one of their development stages.
Chiggers or “red bugs” (called “harvest mites” in Europe) are the larvae of mites belonging to the suborder Trombidiformes. In the Western Hemisphere, the most common and widespread species – ranging from Canada to South America and the West Indies – is Trombicula alfreddugesi.
Chiggers are very small, 150 to 300 microns (0.15 to 0.3 mm) long when engorged, and are red to pale yellow or white, depending on the species. Like all mite larvae, they have six legs. They are parasitic, but later stages are free-living, eight-legged mites. Only the larvae are harmful, and only they are correctly referred to as “chiggers.”
On
humans, chiggers tend to congregate in areas constricted by clothing,
such as ankles, crotch, waistline and armpits.
When chiggers attach to humans they are often not noticed for some
time. This delay is unfortunate, because they can be easily removed.
Infestation symptoms such as red welts and severe itching do not
appear until several hours or even a day after exposure; therefore, it
is difficult to know exactly when or where the infestation occurred.
Life Cycle
The spherical eggs, approximately 0.1 to 0.2 mm in diameter, are usually laid in the soil. Larvae crawl on the soil surface until they find a suitable vertebrae host. They attach to the host by means of their mouth parts and suck blood, but as a rule do not burrow under the skin. Engorgement usually takes about three days. The larvae then drop off, enter the soil, and change to the nymphal stage. The nymphs probably feed on the eggs and young instars of small arthropods.
Favored Habitats
Chiggers are most abundant in undisturbed areas that support thickets or scrub-type vegetation and various small host animals such as rabbits. Chiggers are generally eliminated automatically by habitat destruction in heavily populated or intensively farmed areas. In new urban subdivisions, however, chiggers may persist in lawns for several years.
Control
In
the spring when the eggs hatch and larvae sometimes find human hosts,
doctors can prescribe localized treatment to remedy the itching.
Pesticide applications to lawns are rarely needed.
(Courtesy of the National Pest Control Association.)