Subterranean or Drywood? The Termite Type Changes Everything

"Termite" gets used as if it describes one insect, but subterranean and drywood termites differ enough in basic biology that they leave almost entirely different physical evidence behind. Neither group announces itself the way a visible pest does — both stay hidden inside wood or underground for most of an infestation — so the actual identification usually comes down to recognizing what each type leaves behind rather than ever seeing the insect itself.

The core biological difference: where moisture comes from

The split between the two groups comes down to water. Subterranean termites need regular contact with soil moisture to survive, which is also where their name comes from. Drywood termites tolerate much drier wood and don't need soil contact at all, which is exactly why they can infest wood well above ground — attic framing, furniture, structural beams — with no connection to the earth whatsoever. That single difference in moisture dependency is what produces almost every other distinguishing feature between them.

What drywood termites leave behind: distinctive pellets

Because drywood termites live entirely inside the wood they're consuming, with no outside tunnel system to find, their clearest evidence is what they push out of the wood: fecal pellets. University of Florida and Texas A&M AgriLife Extension describe these pellets as small, roughly a millimeter long, and distinctly six-sided with concave faces — a shape specific enough that it's one of the more reliable ways to confirm drywood termite activity without ever seeing a live insect. They're expelled through small "kick-out holes" in the wood surface, sometimes scattering below in a way that can resemble fine sawdust or sand from a short distance. One genuine point of disagreement among extension sources is worth noting: Texas A&M describes the pellets as generally matching the color of the wood being eaten, while University of Florida and University of Tennessee materials say color has more to do with gut microbes than the wood itself and isn't a reliable identifier on its own. Either way, the six-sided shape under magnification is the real confirmation — university extension guidance also notes that rodent food caches (stored seeds, for instance) can superficially resemble termite pellets but are larger and lack that concave, six-sided structure.

What subterranean termites leave behind: mud tubes

Subterranean termites solve a different problem: getting from moist soil to wood above ground while staying protected and humid along the way. Their solution is the mud (or shelter) tube — a pencil-width tube built from soil and saliva that lets workers travel across open surfaces like concrete or masonry without drying out or exposing themselves to predators. Entomology extension sources describe a few distinct tube types built for different purposes: exploratory tubes sent out searching for new wood sources, permanent utility tubes built once a food source is confirmed, and separate swarming tubes used specifically as an exit route for winged reproductives leaving the colony. One important caveat extension guidance flags: a tube that looks empty or abandoned doesn't necessarily mean the colony is inactive — termites routinely abandon sections of tube while foraging in a different part of a structure, so an empty-looking tube isn't proof the problem has resolved itself.

The exception worth knowing about

The moisture-dependency rule for subterranean termites has a documented exception: if wood and water are both available from some other steady source — a persistent plumbing leak, for instance — a subterranean colony can occasionally establish and survive with no direct soil contact at all. It's an edge case rather than the norm, but it's part of why professional inspection matters even when an obvious soil connection isn't visible: the absence of a classic mud tube running to the ground doesn't automatically rule out a subterranean infestation.

• Subterranean termites require regular soil moisture contact; drywood termites tolerate much drier wood and need no soil connection at all.
• Drywood termite evidence is primarily fecal pellets: roughly 1mm, distinctly six-sided with concave faces, pushed out through small kick-out holes — pellet color is not considered a reliable indicator.
• Subterranean termite evidence is primarily mud/shelter tubes built from soil and saliva, used to travel safely and humidly between soil and wood above ground.
• An empty-looking mud tube doesn't prove a colony is inactive — termites regularly abandon tube sections while foraging elsewhere in a structure.
• Subterranean colonies can rarely establish without soil contact if a persistent alternate water source (like a plumbing leak) is present.

Because the two termite types require different inspection focus and treatment approaches, correctly identifying which one is actually present matters as much as catching the infestation early. A free Sevacorp inspection is a reliable way to get that identification right from the start.

• Sources:
• University of Florida IFAS Extension (EDIS) — "Drywood Termites" (IG098) — https://edis.ifas.ufl.edu/publication/IG098
• Texas A&M AgriLife Extension — "Drywood Termites" — https://www-aes.tamu.edu/files/2010/05/Drywood-Termites.pdf
• Mississippi State University Extension — "Drywood Termite Fecal Pellets" (Bug's Eye View) — https://extension.msstate.edu/newsletters/bugs-eye-view/2020/drywood-termite-fecal-pellets-vol-6-no-21
• University of Arizona Cooperative Extension — "Termites" — https://cales.arizona.edu/backyards/sites/cals.arizona.edu.backyards/files/p9-10.pdf
• Utah State University Extension — "Subterranean Termites" — https://extension.usu.edu/pests/uppdl/files/factsheet/sub-termites09.pdf
• Texas A&M School of Veterinary Medicine, PEER Group — "Subterranean Termite Behavior" — https://vetmed.tamu.edu/peer/termites-background-info