Drywood vs Subterranean Termites: Telling Them Apart

Drywood termites produce 6-sided fecal pellets and attack wood with moisture content below 12 percent while subterranean termites require soil contact, build shelter tubes, and maintain colonies of 1-2 million individuals that need constant moisture above 20 percent.

Distinguishing Physical Characteristics

Drywood termites measure 3/8 inch long with straight antennae and lack the worker caste seen in subterranean species. Subterranean termites include creamy-white workers 1/8 inch long plus soldiers with rectangular heads and curved mandibles. Reproductive forms differ as well: drywood alates are 1/2 inch with dark bodies and wings that extend beyond the abdomen, whereas subterranean alates reach 3/8 inch with pale bodies and shorter wings. These size and shape differences allow visual separation when swarming occurs in spring or fall. Homeowners spotting winged insects near windows can compare wing length and body color against these ranges before assuming the species. Accurate identification guides whether soil treatment or wood injection becomes necessary later.

Fecal Pellets and Frass Evidence

Drywood termites eject small, hard pellets that accumulate in piles beneath exit holes; each pellet shows six concave sides under magnification. Subterranean termites produce liquid frass that mixes with soil into mud, leaving no distinct pellets. A homeowner can collect suspected material on white paper and examine it with a 10x loupe to count sides or note moisture. In older Bay Area homes built before 1950, accumulated pellets often appear first in attics or window frames. Subterranean activity instead shows as brown lines on foundation walls where tubes connect soil to wood. These frass traits remain reliable even when live insects stay hidden inside galleries.

Colony Structure and Moisture Requirements

Drywood colonies stay small, typically 1,000-3,000 members, and survive on wood moisture alone without ground contact. Subterranean colonies expand to 1-2 million workers that forage 300 feet from the main nest and die if separated from soil moisture for more than a few days. Drywood termites digest cellulose with internal protozoa that tolerate low humidity, while subterranean species rely on external fungi and constant dampness. In coastal regions Argentine ant super-colonies do not affect termite survival because they occupy different niches. Central Valley irrigation increases subterranean risk by keeping soil moist year-round. These biological limits explain why drywood damage appears in upper stories and subterranean damage clusters near grade.

Homeowner Actions and Professional Inspection

Source reduction such as storing firewood off soil and fixing roof leaks reduces drywood entry points but cannot eliminate an existing colony. Exclusion with metal mesh on vents helps limit alates yet fails against subterranean foragers that follow utility lines. Only a licensed operator can confirm species through visual tube inspection or moisture metering and apply targeted treatments. Readers can review identification methods in German Roaches vs Everything Else: Telling Them Apart for similar pest comparison skills. Schedule a termite inspection when pellets or tubes appear rather than attempting bait stations or sprays without species confirmation.