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Common chiggers, also known as “jiggers” and “redbugs,” are tiny pests which belie their size in the amount of torment they cause humans. Chiggers attach themselves to tender skin areas to feed. The bites cause intense itching and small reddish welts. Because chiggers are so small, they are hard to avoid. Most persons cannot see them without a magnifying glass and so the bites may be the only indication that the bugs have infested a certain area. Of the major chigger species in Texas, probably only two are annoying to humans. One species lives in upland areas. It likes fields, grass and weed areas, wild berry patches and forest underbrush. Besides humans, it attacks a variety of domestic and wild animals, including birds, reptiles, and some amphibians. The other chigger species prefers moist habitats such as swamps, bogs, rotten logs and stumps. However, both species often live in the same general region.
In the larval stage, chiggers are orange, yellow or light red. They are less than 1/150 of an inch in diameter. Their bodies are hairy. A larva has six legs and its mouthparts include two pairs of grasping palps with forked claws.
The nymphs and adults have eight legs. Their bodies are hairy, about 1/20 of an inch long and usually brilliant red. The front part of their bodies is noticeably smaller than the back.
Biology and Habits
Chiggers are related to ticks and spiders. Their development goes through the same four stages: egg, larva, nymph and adult. Adult chiggers pass the winter in protected places and become active in the spring. The young chigger or larva, which hatches from eggs deposited earlier in the spring, is the real troublemaker. It is a parasite that feeds on man and animals. After feeding for several days, the larva detaches and finds a protected place on the ground where it develops through the nymphal stage into an adult. Under favorable conditions, most chigger species complete their development in 40 to 70 days and produce one to four generations each year in Texas.
Chiggers are active from spring to late fall but are most numerous in early summer when weeds, grasses and undergrowth are the heaviest. Nymphs and adults feed on insect eggs, small insects and other organisms found on or near decaying wood. Larval chiggers congregate in shaded niches near the tips of grass leaves, weeds, sticks and other objects close to the ground. They are activated upon the approach of a suitable host, probably by odor, carbon dioxide output and other stimulating factors, and crawl onto the host for feeding.
Chigger Dermatitis The tiny, bright red larval chigger can scarcely be seen as it scurries along the skin surface seeking an attachment site. When it finds a suitable location, such as a skin pore or hair follicle, it attaches its mouthparts to the spot. On people, the chigger prefers places where clothing fits closely over the skin or where the flesh in thin or wrinkled. Contrary to common belief, it does not penetrate and burrow into the skin or suck blood. Instead, it injects a digestive fluid that disintegrates skin cells so they can be used as food. A feeding “tube” formed by the chigger secretion and skin cells of the host permits the chigger to extract food until it is engorged. After leaving the host, it undergoes further development on the ground.
Affected skin tissue becomes red and swollen. It may completely envelop the feeding chigger, making the chigger appear to be burrowing into the skin. Chigger bites have a more severe effect on some persons than others. The bite itches intensely and may continue itching for several days after the chigger is killed or drops off. The itching probably results from the digestive action of the enzymes injected by the larva into the skin.
Protection Several commercially available repellents are effective against chigger infestations. These repellents usually contain one or more of the following compounds: permethrin, diethyl toluamide, dimethyl phthalate, dimethyl carbate, ethyl hexanediol and benzyl benzoate. Most repellents are also effective against mosquitos and other insects. They are formulated as liquids, aerosol sprays, solid sticks and ointments. Common dusting sulfur, although somewhat messy and odorous, is also a very effective repellent.
Repellents should be used according to instructions. Usually, they provide protection from chiggers for several hours. For protection which lasts several days, saturate clothing by soaking or spraying it with a repellent solution. For further prevention, wear loose-fitting clothing and avoid sitting or reclining on the ground when camping, picnicking, or working outdoors.
Reducing the Itching Immediately after exposure to chigger-infested areas, take a hot bath to kill and remove chigger larvae. Then apply an antiseptic solution to any welts that have appeared to kill trapped chiggers and to prevent infection. Destroying the chigger usually does not stop the itching completely because the itching is caused by tissue reaction to the fluid injected by the chigger. Normally, two to three days pass before the itching stops. Temporary relief can be obtained by applying a commercial product that contains a mild, local anesthetic. Your pharmacist can suggest an appropriate product for your needs.
Any unusual allergic reaction, fever or infection should be treated by a physician. Control
Control of chiggers in large parks, recreation areas or campgrounds is impractical. Personal protection with repellents when visiting such areas is the best means of reducing chigger bites. Chiggers sometimes become a problem in home lawns, particularly those with Bermuda grass, and chemical control may be desirable. Several granular and spray formulations containing diazinon or chlorpyrifos (Durisban®) are effective against chiggers and other lawn pests. These are sold by nurseries, garden supply stores, farm supply outlets and other retail establishments. Insecticide label clearances are subject to change and changes may have occurred since this publication was printed. The pesticide USER is always responsible for the effects of pesticide residues on his own plants or household goods as well as problems caused by drift from his property to other properties or plants. Always read and follow carefully the instructions on the container label.
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