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Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

Tiny red spots before my eyes: Clover mites, Bryobia praetiosa


Eight tiny legs help clover mites scuttle across a sidewalk.


A fine patch of clover spawns a fine crop of clover mites in my lawn.

In last week’s episode we met a gorgeous male Luna moth stranded on a sidewalk. This week we turn to another sidewalk to meet yet another fascinating arthropod making its presence known as spring turns into summer. Who knew sidewalks could be so interesting? Glancing down at my sidewalk I spotted a few tiny red spots wandering in seemingly random patterns across the flagstones. A closer inspection revealed these scarlet miniatures to be eight legged creatures known as clover mites. Clover mites are plant feeders, so named for their fondness for clover although other common garden plants, including grasses, dandelions, wild strawberries and several other ornamental trees and shrubs, are definitely on their menu. Their feeding and damage to plants is often concentrated on the sunny sides of homes and businesses where temperatures are higher and mite development is elevated.

White stipples on leaves of plants like clover mark the spots where clover mites have ruptured cells and removed the green tissue within.

Like the rest of their kin, clover mites use tiny piercing mouth parts to rupture cells of plants, releasing nutritious fluids that are slurped-up into their digestive tract. This mode of feeding produces tiny white spots on leaves, a type of injury known as stippling, yes, just like the technique used by artists to create contour in illustrations. Plant sap sustains the mites and enables the successive immature stages known as larvae (which have only six legs), protonymphs, and deutonymphs to develop into adults. Each female may lay as many as many as 70 eggs, either in clusters or one by one. The clover mites we see in this season spent the winter as eggs deposited by females last autumn. They hatched in March and April and have been feeding in lawns and landscapes. One reference notes that clover mites often become pests following periods of heavy rain, excessive heat or a change in season, all events that have transpired in the DMV over the past few weeks. Clover mites will have several generations in our region until the summer turns hot and dry, at which time they enter a period of inactivity called aestivation. With the return of cooler, moister weather in autumn they may become active and abundant again.

When squashed on a wall or curtain, clover mites generate a rather remarkable and somewhat imaginative reddish stain.

If you find clover mites inside your home, please don’t try to sweep them away. Their tiny red bodies are easily crushed and following the explosion you will find their not so tiny scarlet signature on your wall or curtain. To avoid this mess, simple take your hand-held vacuum, hold it slightly above the mite, and levitate them to their demise. One way to reduce the number of clover mites entering a home or business is to remove grass, weeds, and other herbaceous plant material near the foundation. Create a no man’s land, or should we say a no mite’s land, of crushed stone or pea gravel a few feet wide around the foundation. This barrier will help reduce invasions not only by clover mites, but also other ground dwellers like millipedes and pill bugs we met in previous episodes. Foundation plantings of yew and juniper are not attractive to clover mites. Neither are many flowers including mums, marigolds, salvias, and geraniums. Over the next several weeks, don’t be surprised if you see tiny red dots before your eyes and clover mites make their presence known on sidewalks, siding, and sometimes in homes.  

At dusk on a sidewalk, what does a lonesome clover mite seek?


Bug of the Week thanks John Kelly for inspiring this episode. Two wonderful references, “Destructive Turfgrass Insects” by Dan Potter, and “Clover mite, Bryobia praetiosa Koch (Arachnida: Acari: Tetranychidae)” by Celina Gomez and Russell F. Mizell, were used to prepare this episode. Thanks to Dr. Paula Shrewsbury for handy camera work capturing an image of a fast moving clover mite.