Texas is home to several millipede species, from the small greenhouse millipede that invades homes by the hundreds to the impressive desert millipede that can reach 9 inches long. None of them bite, and they’re generally harmless to people, though they can secrete irritating chemicals when handled. Most Texans encounter millipedes after heavy rain or during dry spells, when these moisture-dependent creatures wander indoors looking for better conditions.
Common Species in Texas
The most frequently encountered millipede in Texas homes is the greenhouse millipede (Oxidus gracilis), a small, dark brown species that thrives in moist environments. It’s the most commonly managed millipede pest in the state. Outdoors, it lives in garden mulch, compost piles, and leaf litter. Indoors, it gravitates toward bathrooms, basements, and kitchens.
In west Texas, you’ll find the American giant millipede (Narceus americanus), which grows up to 4 inches long. This species is relatively common in wooded and semi-arid areas across the state.
The most striking species is the desert millipede (Orthoporus ornatus), found in the arid western portions of Texas, including Big Bend National Park. These millipedes average about 4 inches in length but can grow anywhere from 3 to over 9 inches. They’re typically dark brown, sometimes with yellowish coloring, and can live more than 10 years. In Big Bend, they feed on native plants like honey mesquite and ephedra shrubs, processing 20 to 37 percent of the plant material they consume into nutrients that cycle back into the soil.
Why Millipedes Enter Texas Homes
Millipedes need moisture to survive. Their bodies lose water quickly, which makes them sensitive to any shift in outdoor humidity. Two opposite weather events push them indoors: drought and heavy rain.
During dry spells, especially in the Texas summer, millipedes migrate toward buildings to find the moisture they’ve lost outdoors. During periods of excessive rainfall or flash flooding, they move indoors to escape waterlogged soil and seek higher ground. Either way, the result is the same: you find them clustered in damp areas of your home, sometimes in startling numbers. Greenhouse millipedes in particular have been documented invading homes by the hundreds or even thousands.
The good news is that millipedes don’t typically survive long indoors. The air inside most homes is too dry for them, and they usually die within a few days without a sustained moisture source.
Are Texas Millipedes Dangerous?
Millipedes do not bite. They lack the mouthparts to pierce human skin. They also don’t sting. What they can do is secrete a chemical called benzoquinone from glands along their body segments. This compound is their defense against predators, and it can irritate your skin if you handle a millipede or accidentally crush one.
On human skin, benzoquinone causes localized color changes, typically dark red, blue, or black patches, most commonly on the feet and toes if you step on a millipede barefoot. These spots can look alarming, resembling burns or bruises, and may come with a burning or itching sensation. There are no known reports of the chemical causing body-wide effects. The discoloration resolves on its own over time.
The bigger concern is your eyes. If you handle a millipede and then touch your face, the secretion can cause redness, swelling, and pain. Rinsing with water is the immediate step if this happens. As a general rule, wash your hands after picking up any millipede, and avoid letting children or pets mouth them.
Their Role in Texas Ecosystems
Millipedes are decomposers. They eat dead leaves, decaying wood, and other organic matter on the ground, fragmenting it into smaller pieces and passing it through their digestive systems. Their droppings break down faster than the original leaf litter in many cases, which accelerates the cycling of carbon and nitrogen back into the soil. They also increase the amount of available phosphorus in soil, a nutrient essential for plant growth.
In ecosystems like Big Bend, where organic material is scarce and decomposition is slow, millipedes play an outsized role in keeping nutrients moving. They’re one of the primary organisms responsible for breaking down tough, dry plant material that bacteria and fungi alone would process much more slowly.
How to Keep Millipedes Out of Your Home
Reducing moisture around your home is the single most effective strategy. Direct water runoff away from your foundation, fix leaking pipes, and eliminate standing water from irrigation or air conditioner condensation. If your home has a crawlspace, installing a plastic vapor barrier over the exposed soil cuts off a major moisture source that attracts millipedes.
Physical exclusion comes next. Seal cracks and crevices in your foundation and exterior walls. Caulk around window frames, door frames, and thresholds. Install door sweeps on exterior doors. Block weep holes with steel wool, then seal the steel wool in place with caulk or expanding foam. Fill gaps around drainpipes and vents the same way. Inside, check behind baseboards in rooms with damp floors, as millipedes will tuck into those gaps.
For additional protection, diatomaceous earth powder can be applied to entry points like cracks, crevices, weep holes, and gaps around pipes. It works by damaging the millipede’s outer coating, causing it to dehydrate. For larger perimeter treatments, residual insecticides can be applied in a 5- to 20-foot band around your home’s foundation and around entry points. Look for products containing bifenthrin or cyfluthrin, which are commonly available at hardware stores for outdoor perimeter use.
If you’re finding millipedes inside but only a few at a time, the simplest response is to pick them up with a tissue or vacuum them. They’ll die on their own indoors within days. A mass invasion, with dozens or hundreds appearing at once, usually signals a moisture problem worth investigating around your foundation or landscaping.