Brick bugs are tiny red or reddish-brown mites that swarm on brick walls, concrete patios, and masonry foundations, especially in spring. They’re not actually insects at all. They’re arachnids, related to spiders, with eight legs instead of six. The two species most commonly called brick bugs are clover mites and concrete mites, and neither one bites humans or causes structural damage.
What You’re Actually Seeing
Two species account for nearly all sightings of small red creatures on brickwork and concrete. Telling them apart helps you understand what to expect and whether you need to do anything.
Concrete mites (genus Balaustium) are bright red, very fast, and tend to scurry between textured surfaces like embedded pebbles and rough masonry. They’re almost exclusively found on concrete, stonework, and foundation walls, never on plants or in grass. They leave a red dye when crushed but don’t bite. Concrete mites are actually beneficial predators that eat other tiny mites and insects in the landscape. They typically appear in large numbers during April and May, then disappear for the rest of the year.
Clover mites (Bryobia praetiosa) are slightly different. They’re reddish-brown to dark greenish-brown, oval-shaped, and roughly 0.75 to 0.85 mm long, appearing as tiny moving dark spots to the naked eye. Their most distinctive feature is a pair of front legs about twice the length of the other six, often mistaken for antennae. Unlike concrete mites, clover mites feed on clover and other plants and use brick walls as a highway to find warm spots and entry points into buildings. They’re most active in spring but can show up during any warm stretch throughout the year.
Why They Gather on Brick and Masonry
Brick, concrete, and stone absorb and radiate heat from the sun, creating a warm microclimate that both species are drawn to. Concrete mites seem to prefer these surfaces as their primary habitat, feeding on pollen and tiny organisms they find in the textured crevices. Clover mites use sun-warmed walls as a migration route. They move upward as the surface heats, searching for sheltered cracks and gaps. If the surface gets too hot or too cold, they roam until they find a more comfortable spot, which sometimes leads them straight through window frames and door gaps into your home.
South-facing and west-facing walls tend to see the heaviest activity because they get the most direct sunlight. You’ll often notice the biggest swarms on warm mornings in spring after a stretch of cooler weather.
Do Brick Bugs Bite or Cause Damage?
Clover mites never bite humans and don’t damage property. Concrete mites don’t bite either. Neither species transmits disease. The only real problem they cause is cosmetic: both leave reddish stains when crushed. On light-colored walls, curtains, or upholstery, these stains can be surprisingly noticeable and difficult to remove.
In rare cases, large populations of mites in the home can trigger mild allergic reactions in sensitive individuals, similar to dust mite allergies. This is uncommon and typically only a concern when mites have been entering a home in significant numbers over time.
People sometimes confuse brick bugs with chiggers (also called redbugs), which do bite. Chiggers are a completely different mite that lives in grass and brush, not on masonry. Chigger bites inject digestive enzymes into the skin, causing intense itching that starts 3 to 6 hours after exposure and can last up to two weeks. If you’re finding red mites on brick walls and concrete, they’re almost certainly not chiggers.
What About Masonry Bees?
Some people searching for brick bugs are actually noticing small bees nesting in mortar joints. Masonry bees are solitary bees that use pre-existing holes and crevices in brickwork, old nail holes, or gaps under roof tiles. They don’t typically cause significant structural damage because they’re exploiting gaps that already exist rather than boring into solid material. Some females can dig into soft, crumbling mortar with their mandibles, but this is minor. If your mortar is in good condition, masonry bees aren’t a structural concern.
Removing Brick Bugs Without Staining
The biggest mistake people make is crushing the mites, which smears red pigment across whatever surface they’re on. Instead, use a damp soapy rag or wet sponge and gently wipe them up without pressing hard. A vacuum cleaner with a crevice attachment also works well for collecting mites from windowsills, door frames, and wall surfaces without leaving stains.
For mites already inside, this gentle removal is usually all you need. Concrete mites in particular are only around for a few weeks in spring, so the problem resolves on its own.
Keeping Them Out of Your Home
Since clover mites actively seek entry points into buildings, sealing gaps is the most effective long-term strategy. Start with the places they’re most likely to get through:
- Door bottoms: Install door sweeps on all exterior doors. Lie on the floor and check for light coming under the door. Gaps as small as 1/16 of an inch are enough for mites to enter. Apply caulk along the bottom outside edge of door thresholds.
- Windows: Caulk cracks around window frames using silicone or acrylic latex caulk. Repair any torn or gapped window screens.
- Utility openings: Seal gaps where pipes, wires, and vents enter the foundation. Outdoor faucets, gas meters, dryer vents, and cable lines all create entry points. Use caulk, cement, or expandable foam to plug them.
- Sliding doors: Line the bottom track with half-inch to three-quarter-inch foam weatherstripping to close the gap.
- Garage doors: Fit them with a rubber bottom seal. Vinyl seals become rigid and ineffective in cold weather.
Creating a vegetation-free border around your foundation also helps with clover mites specifically. Since they feed on clover and grass before migrating to walls, a band of bare gravel or mulch 18 to 24 inches wide between your lawn and the foundation reduces the number of mites that reach the building in the first place.
When Spraying Makes Sense
For most people, sealing entry points and keeping vegetation away from the foundation is enough. If mites are entering in large numbers despite those steps, an exterior barrier spray around the foundation can help. Apply it at the base of exterior doors, around foundation vents and utility openings, up underneath siding, and in a band 2 to 6 feet wide along the ground at the foundation perimeter. Longer-lasting liquid formulations work better than quick-knockdown sprays for this purpose.
For concrete mites that stay outdoors on patios and walkways, spraying is rarely worthwhile. They’re present for only a few weeks, they’re beneficial predators in the landscape, and they don’t enter homes the way clover mites do. A strong blast from a garden hose will clear them temporarily if they’re bothering you during outdoor activities.