By Bill Willis and John McLamb
July 3, 2018
Each spring, very small, bright red “bugs” were observed crawling on the campus concrete patio walls and planters. They seemed to like the sunshine as they run between the embedded pebbles. We’d seen them for many years, but never had a conclusive identification. Initially thought to be clover mites, web searches revealed that they might be concrete/sidewalk mites (Balaustium sp.), which looked similar to the clover mite (Bryobia praetiosa).
They're fast, hard to see, and emit a red dye when squished, but no one has complained about getting bitten. The front pair of legs is longer than the second pair for both the clover and concrete mites. These red mites were not seen anywhere but on the masonry, and not on clover or surrounding vegetation. That was the same observation made by bugguide.net that these mites were found on foundation walls, stonework and concrete sidewalks.
Mites are kin to spiders and not insects, for they have four rather than three pairs of legs as adults. That makes them arachnids instead of true insects. The life cycle of mites is variable. Early stages may be parasitic while later ones are predatory depending on the species. Some mites begin as pollen eaters, and then become predatory or parasitic on other mites, small insects, birds and even mammals in later life stages.
Reports out of Florida would support the identification as a member of the predatory Balaustium mites that are fairly common in the United States. That would make them actually beneficial mites in the landscape. Since these mites are here a short length of time (April – May), there is no need to control unless they invade the home.