The appearance of tiny, bright red specks scurrying across sidewalks and patios often leads to the question of whether these creatures are the dreaded chiggers. This confusion stems from their small size and reddish color, prompting concern about painful bites. The simple answer is that the red mites found on concrete are not chiggers; they are different species that pose no threat of biting humans. Understanding the distinct biology and behavior of these two organisms is key to distinguishing a harmless nuisance from a genuine pest.
Identifying the Mites Seen on Pavement
The tiny, fast-moving red arachnids frequently observed on sun-warmed surfaces are usually either Clover Mites (Bryobia praetiosa) or Concrete Mites (Balaustium species). Clover mites are oval-shaped and reddish-brown, measuring about 0.75 to 0.85 millimeters long. They are plant feeders, consuming sap from grasses, clover, and ornamental plants using piercing-sucking mouthparts. They are considered nuisance pests because they migrate in large numbers, often appearing on foundation walls or entering homes during the spring and fall.
Concrete mites (Balaustium) are slightly larger, up to 1.5 millimeters, and are a brilliant red color with a velvety texture. They congregate on concrete, stone, and masonry, where they are primarily generalist predators of small arthropods and insects. They also feed on wind-blown pollen and algae. Neither species bites people or pets, and any red stain left by crushing them is pigment, not blood.
The Biology and Habitat of True Chiggers
The creature responsible for the itchy red welts is the larval stage of a mite belonging to the Trombiculidae family, commonly known as chiggers or harvest mites. These larvae are minuscule, measuring under 0.5 millimeters, and possess only six legs, unlike the eight-legged nymphs and adults. Chiggers are not found on concrete; they inhabit dense vegetation, tall grass, wooded areas, and damp, shaded spots, waiting for a host.
The larval chigger is the only parasitic stage in the life cycle and attaches itself to a passing vertebrate host. They do not burrow into the skin or suck blood. Instead, the larva pierces the skin and injects a salivary secretion containing digestive enzymes that break down skin cells. The chigger then feeds on this liquefied tissue for several days before dropping off to continue its development.
Why They Are Not the Same
The most significant distinction between pavement mites and chiggers lies in their feeding behavior. Pavement mites are herbivores or predators that target plants, pollen, or other tiny insects, making them harmless to human skin. Chiggers, conversely, are parasites that feed on the dissolved skin cells of animals, causing a noticeable and irritating reaction. This difference in diet dictates their respective threat levels: pavement mites are merely a nuisance when crushed, while chiggers cause dermatitis.
Their preferred habitats are also mutually exclusive. Chiggers require the moist, shaded environment of dense vegetation to survive and wait for a host. Pavement mites are often drawn to the dry, sunny conditions of hard masonry surfaces, which would be inhospitable to a chigger larva. Finally, adult pavement mites always have eight legs, while the stage that attacks vertebrates, the chigger larva, is exclusively six-legged.
Controlling Pavement Mite Populations
Managing the red mites found on concrete involves targeting their habitat and points of entry. A simple, non-chemical control method is to use a strong jet of water from a garden hose to wash the mites off walls and foundation areas. This physical removal reduces their numbers and washes away algae or pollen they may be feeding on.
Creating an exclusion zone around the home foundation is an effective preventative measure. This involves establishing a plant-free barrier, typically 18 to 24 inches wide, filled with a material they struggle to cross, such as pea gravel, lava rock, or mulch. If mites enter indoors, they can be safely removed by vacuuming, but crushing them should be avoided to prevent red staining. Chemical control, when necessary, involves applying a residual insecticide around the foundation perimeter, windows, and doors to create a lasting barrier.