Chigger Mites

Facts, Identification & Control

Scientific name

Trombicula spp.

There are many species of chiggers located within the united states, but the most common species encountered by people are trombicula alfreddugesi and trombicula splendens.

Appearance

Chigger larvae are very small, about 0.15 to 0.25 mm long, are red to reddish orange in color with six legs. Chigger adults are larger than the nymphs and larvae, being about 1 mm (@ 1/25th inch long) and bright red. Both nymphs and adults have eight legs.

Behavior, diet & habit

Chigger mites develop by going through 4 distinct life stages – eggs, larvae, nymphs and adults. The life cycle begins when the female adult lays eggs in or on the soil. After the eggs hatch, larvae crawl upon the soil surface and low growing vegetation where they wait until they find a suitable host to attach to and begin to feed. The larval stage is the only parasitic stage of the mite’s life cycle.

Preferred hosts of the larval chigger mites are people, snakes, birds and many species of small mammals. The chigger mite larva penetrates the host’s skin and injects a secretion that breaks down and digests the skin cell . The larvae then suck up the digested liquid. As the larvae feed, the host’s skin becomes hard and a tube forms in which the chigger’s mouthparts remain until feeding stops or the chigger is dislodged. Chigger larvae to do not burrow into the skin or suck blood as do ticks and some other species of parasitic mites.

The body’s reaction to the secretions of the mites is what causes the itchy, red bumps on human skin. Chigger bites and the associated itching are usually located around the ankles, legs, along the tops of socks, behind the knee, around the waist and other places where clothing fits tightly against the body. In addition, chiggers may sometimes travel to the groin area before stopping to begin feeding. Generally, chigger larvae feed several days if not dislodged, drop to the ground and develop into mite nymphs.

Nymphs and adults do not infest the same hosts as the larvae; instead, they feed on the eggs and young of insects and other small arthropods in and on the soil surface. Depending upon the temperature and other environmental factors, chigger mites complete one life cycle in about 2- 3 months. In favorable climates, they may complete 3 generations per year.

Preferred chigger mite habitat are areas of thick, scrub-type vegetation, grassy areas where the soil is undisturbed and they can “latch” onto hosts that may be passing by. Generally, chigger mites are found in rural, less disturbed areas, but can persist for several years in their habitat associated with new housing subdivisions.

Reproduction

Male trombicula alfreddugesi fertilize the females in a very interesting manner. Adult males of the species move around their preferred habitat and deposit very tiny capsules of sperm known as spermatophores that the adult females will find and insert into a structure on their body known as the genital pore. A bout two weeks after fertilization of the eggs, the female drops her fertilized eggs onto the soil surface.

Signs of a chigger mite infestation

The symptoms that occur from the feeding activity of chigger mite larvae are generally the most obvious sign of an infestation. In addition, the appearance of nymphs and adults in or on the soil and vegetation also can signal the presence of chigger mites. However, chigger mites are so small that actually seeing any stage of this mite is difficult.

Distribution

Trombicula alfreddugesi and splendens are common in the southeastern and midwestern states, plus some areas in the Great Lakes and the Mississippi River valley regions. However, even in areas of preferred habitat, chigger populations may be sparse in one area and very heavily concentrated in a nearby area.

More information

Chigger management is generally a task best suited for your pest management professional (pmp) since it is so difficult to determine the source of the problem. Your pmp will be familiar with techniques that work to inspect for and locate chigger mites and will target the areas where chiggers are abundant rather than using chemical products throughout the entire property. Also, his knowledge about chigger habitat and habitat modification will be valuable to reduce the places where chiggers can successfully live and develop.

Other information:

  • When venturing into the woods or other areas where chiggers are located, wear clothing treated with permethrin clothing repellent. Also consider applying insect repellent to parts of your body where chigger larvae may infest.
  • Although very irritating, chigger mites in north america are not disease carriers.
  • Itching caused by chigger bites does not occur until about three or more hours after the bite.
  • The red welt on the skin is not where a chigger laid eggs.
  • Chiggers can infest dogs and cats.

The more common locations for chiggers to bite and feed are the legs, head and abdomen. For cats, chiggers may be found on the inside of the animal’s ears. The reaction of dogs and cats to chiggers range from scratching at the site of infestation to the animal being unaware of the chigger’s presence. People do not get chiggers from contact their pets; rather, chiggers on both pets and people almost always mean that both were outside in areas where chiggers were numerous.