Three main types of termites cause structural damage in the United States: subterranean, drywood, and dampwood. Each behaves differently, lives in different conditions, and leaves behind different evidence. Knowing which type you’re dealing with matters because the signs of infestation, the severity of damage, and the approach to control vary significantly between them. Collectively, termites cost U.S. residents an estimated $5 billion a year in control and repairs.
Subterranean Termites
Subterranean termites are the most widespread and destructive type in the country. They’re found in every state except Alaska, and they live and breed in soil, sometimes nesting many feet below the surface. Mature colonies can contain hundreds of thousands of individuals. These termites require constant moisture, so they maintain a connection to the soil even when feeding on wood above ground. They do this by building mud shelter tubes, pencil-width tunnels made of soil and saliva, that run along foundation walls, support piers, or plumbing to reach the wood in your home.
The telltale sign of a subterranean termite problem is finding these mud tubes on your foundation, crawl space walls, or support beams. You might also notice small, BB-sized spots of dried mud on interior walls or ceilings. These “pinholes” form when termites accidentally break through a surface and quickly patch the opening because they can’t tolerate open air. Subterranean termites are smaller than drywood or dampwood species, but their massive colony sizes make them far more destructive overall.
Formosan Subterranean Termites
Formosan termites deserve special attention. Originally from East Asia and first detected in the continental U.S. in port cities along the Gulf Coast in the 1960s, they’re considered one of the most aggressive and economically devastating termite species in the country. A typical Formosan colony can exceed one million insects, dwarfing native subterranean colonies. That size translates directly into speed: they cause the same type of damage as other subterranean termites, just much faster.
What makes Formosan termites especially problematic is their flexibility. While they nest underground like other subterranean species, they also build aerial nests inside structures using chewed wood, soil, saliva, and fecal material. These carton nests can grow to several cubic feet. Having both a subterranean nest near the building and an aerial nest inside it dramatically increases the damage potential. Formosan termites have also been known to chew through non-wood materials, including thin sheets of soft metal, plaster, rubber, and plastic, in their search for food and moisture. They attack more than 47 plant species and are responsible for an estimated $1 to $2 billion in annual control costs and repairs in the U.S. alone.
Their mud tubes tend to appear higher on buildings than those of native subterranean termites. If you see shelter tubes on exterior walls, soffits, or fascia boards, or odd mushroom-shaped mud formations sprouting from walls or ceilings in late spring, those are likely signs of Formosan activity. The formations are “swarm castles” built in preparation for their mating flights.
Drywood Termites
Drywood termites live entirely above ground inside the wood they eat. They don’t need soil contact and don’t build mud tubes. Instead, they extract all the moisture they need from the wood itself, which means they can infest structural lumber, dead tree limbs, utility poles, decks, fences, and even furniture. In structures, they tend to nest under wooden roof shingles, eaves, or siding.
Their geographic range is more limited than subterranean termites. Drywood termites cause significant damage in the Atlantic coastal states south of Virginia, throughout Florida, along the Gulf Coast, near the Mexican border, and along the Pacific Coast up to just north of San Francisco.
The signature sign of drywood termites is their fecal pellets. Because they live entirely within wood, they push dry, sand-grain-sized pellets out through small “kick-out holes” in the surface. These pellets are roughly 1/32 of an inch long, with six flattened sides visible under magnification, and tend to be blunt at one end and pointed at the other. They accumulate in small piles on floors, countertops, or windowsills below the infested wood, and they’re usually the color of whatever wood the termites have been eating. Finding these distinctive piles is often the first clue to an infestation.
Dampwood Termites
Dampwood termites are the largest of the common species. Pacific dampwood soldiers measure about three-quarters of an inch long, and reproductive adults can exceed one inch including their wings. Despite their size, they’re considered minor structural pests compared to subterranean and drywood termites. They thrive in wood with high moisture content, especially stumps, fallen trees, and any structural wood affected by water damage.
Soil contact isn’t necessary for dampwood termites, but any condition that keeps wood damp can invite them. Leaky pipes, poor gutters, rain-soaked firewood stacked against a house, and support beams in poorly ventilated crawl spaces are common entry points. Once established, they can extend their feeding into sound, relatively dry wood nearby. Their range is largely limited to the Pacific Coast (from Baja California to British Columbia), the desert Southwest, and southern Florida. The Pacific dampwood termite is most common along coastal areas of Oregon, Washington, and California, while the Nevada dampwood termite extends into colder, higher elevations in the Sierra Nevada and Rocky Mountains.
Finding dampwood termites in a structure is a strong indicator of a moisture problem or active wood decay. They carve large, open galleries inside the wood where they live and feed. Solving the moisture issue is typically the most important step, since these termites can’t survive in dry wood.
Termite Castes Within a Colony
Regardless of type, every termite colony is organized into three castes: workers, soldiers, and reproductives. Workers are the largest group, soft-bodied and wingless. They do everything: gather food, care for young, build tunnels, and maintain the nest. Soldiers are fewer in number but larger, with oversized heads and powerful jaws built for defending the colony against ants and other invaders. Some species have soldiers that lack jaws entirely and instead spray defensive chemicals from a gland in their head. Soldiers can’t feed or groom themselves and depend entirely on workers.
The only true adults in a colony are the king and queen. The queen lays eggs continuously, producing new workers and soldiers as the colony grows. Once a colony matures, it produces winged reproductives called swarmers that leave the nest on a brief mating flight. After landing, their wings break off, and each mated pair attempts to start a new colony. Seeing a swarm of winged termites near your home, or finding discarded wings on windowsills, is one of the most visible signs that a mature colony is nearby.
Swarmers vs. Flying Ants
Termite swarmers are frequently mistaken for flying ants, but three quick features tell them apart. Termites have straight antennae, a broad waist with no pinch, and two pairs of wings that are equal in length and clear. Flying ants have elbowed antennae, a distinctly pinched waist, and two pairs of brown-tinted wings where the front pair is noticeably larger than the back. Termite swarmers also tend to be uniformly black or dark brown, while flying ants can be black, brown, or reddish.
Where Each Type Is Found in the U.S.
Subterranean termites have the broadest range, present in every state except Alaska, including elevations above 8,000 feet. They’re the primary termite threat for the vast majority of U.S. homeowners. Drywood termites are concentrated in warmer coastal and southern regions: Florida, the Gulf states, southern Atlantic states, the Southwest border, and coastal California. Dampwood termites have the narrowest distribution, mostly along the Pacific Coast with pockets in the desert Southwest and southern Florida. Hawaii deals with all three types, including well-established Formosan subterranean termite populations that have been present since around 1850.
Formosan subterranean termites were first reported on the U.S. mainland in Gulf Coast port cities in the 1960s and have since spread to isolated areas of Alabama, Mississippi, Texas, Tennessee, Georgia, North Carolina, South Carolina, Florida, and a small area near San Diego in California. Their range continues to expand, and any region with warm, humid conditions is potentially at risk.