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Drywood Termite

Introduction

Unlike subterranean termites which require excess moisture, drywood termites spend almost their entire life cycle inside the sound, dry wood members upon which they feed. Only during brief swarming flights do young adults leave the confines of their galleries to begin new colonies elsewhere. Winged adults or “swarmers”, shed wings, ejected pellets, and galleries inside wood are typical signs of a drywood termite infestation. Swarming ants are sometimes confused with termites, but their differences are easy to recognize.

Life Cycle and Biology

Drywood termites, like all termites, are eusocial insects. They live in colonies and cooperatively care for young. Responsibilities for reproduction, foraging and colony defense are divided up among castes: reproductives (king, queen and alates), workers and soldiers. In drywood termites, the “worker” caste does not consist of true workers that are reproductively sterile and found in the higher termites of the family Termitidae. Rather, immature termites do the labor of the traditional worker caste, and they are known as pseudergates (“false workers”). All the castes have chewing mouthparts, although the mandibles of the soldiers are greatly modified for defense to the point that they must be fed by the pseudergates. All but the reproductives are blind.

After the eggs hatch into larvae and go through about three molts, the young begin the process of separating into castes. Some molt into presoldiers, which resemble soldiers in form but are unsclerotized and thus white in color. Others become nymphs, which will eventually develop into winged reproductives, or alates. Other larvae molt to become the worker class of the colony, taking care of excavating galleries keeping the soldiers fed. Drywood termite pseudergates are different from subterranean termite workers in that they can continue to develop into alates should a need arise in the colony. In the family Termitidae, workers are sterile adults, and the path to that caste is a one-way street. Once a worker, always a worker.

Eventually, nymphs molt into alates. Swarms occur when these alates leave the colony to start new colonies elsewhere. Cryptotermes cavifrons is an unusual species in that alates are present in colonies throughout the year. Swarms occur in the evenings all year long, but the peak swarming time is March through May. Termites are weak fliers and tend to flutter about on the wind as much as actively fly. It is likely that they will not stray too far from the original colony in their dispersal flights.

When alates land, they twist off their wings, find a mate and burrow into a suitable location in the wood such as a knothole or crevice and mate. Alates who have broken off their wings are called dealates. Eggs then take several months to hatch.

Drywood termite colonies develop slowly. The entire colony may take five years or more to mature. Limited space and resources prevent them from even attempting the rapid growth of subterranean colonies. Even with optimal resources, the growth rate of drywood colonies is slow due to their low inherent reproductive rate. Drywood termites’ legs are actually shorter than subterranean termites’ legs, as well, and they literally move slower as a result. Also, in their preferred habitat, water is a precious resource in limited supply at certain times of the year. Drywood termites have several adaptations for conserving as much water as possible. Three pairs of rectal glands compress their feces to remove and retain all water possible before waste excretion. This results in hexagonal fecal pellets (frass). These six-sided pellets, usually found in small piles, are indicative of drywood termite infestation. In C. cavifrons termites, the pellets are small and feel like grains of coarse sand when rubbed between the fingers. Drywood termites depend heavily on production of metabolic water.

Damage

External signs of damage are elusive with drywood termites. Often, the only obvious signs of infestation are little mounds of fecal pellets building up underneath the infested wood or the appearance of “kick-out” holes in the surface of the wood. Drywood termites make tiny holes in the surface of the wood that allow them to expel their fecal pellets. Cryptotermes cavifrons soldiers can quickly plug the holes with their phragmotic heads if necessary. Some holes also may be closed off with a temporary paperlike substance. These holes are usually very difficult to see because they are very small (about 1 mm) and seldom open. The diameter of the frass piles is proportional to the height of the kick-out holes. Homeowners frequently mistake frass piles for sawdust.