As its name means, this type lives underground, building colonies in damp regions wherever a source of wood (its main food) is available in the soil. The colony reproduces rapidly; then, as its population increases, worker termites are sent out in search of other sources of food. They prevent exposure to both daylight and open air and, if possible, will work their way into the wooden structure of nearby houses without exposing their supply lines.
Since termites can’t survive except under moderated conditions of moisture and temperature, they’ll never expose themselves to the drying effect of open air, except on swarming time in the spring. Termites will burrow through the soft parts of an entire wood beam without breaking through to the outside. As an outcome, the destructive effects can sometimes go absolutely unnoticed until the damage is so serious that complete crumble takes place. Nonetheless, this type of damage would take a lot of years, so even when an infestation is ultimately detected, there’s no need to panic or to act hurriedly.
Wherever possible, subterranean termites will work below the surface of the ground to bore into those wooden members which come in direct contact with the soil. Still, these ingenious insects will also build up mud tubes or tunnels through gaps in masonry foundations, through the hollow cores of cement blocks and even on the surfaces of metal pipes, foundation walls and similar surfaces. In extreme cases, termites have even been recognized to build tubes straight up—unsupported —to bridge from the ground in a damp crawl space to wooden beams overhead.
The mud like tubes or tunnels named above vary in size from 1/2 to 1 1/2 inch in width, and they’re half-round in cross section. They enable the termites to travel to and fro from the underground colony to the wooden structure without exposing themselves to sunlight or open air. The termites need to return to the ground at least once a day to refill their supply of moisture and to bring food to the other members of the colony.
When a colony becomes large enough, warm weather is the sign for the younger kings and queens, the reproductive members of the colony, to fly out in their yearly attempt to establish new colonies. On this period they fly about in the open air on mating flights, then cast off their wings before settling for good into their new underground homes.
It’s the appearance of a swarm of these flying insects or of a multitude of discarded termite wings near a wall that frequently gives the homeowner his first warning that one or more established termite colonies are situated nearby. In some cases these swarms may be mistaken for flying ants, since both insects appear similar to the uninitiated eye. Actually, the deviation in appearance is quite pronounced. The termite has a relatively straight, oblong body of equal thickness along its total length. The ant has an hour-glass-shaped, segmented body which is linked up in the center by a thin, wiry stem. Termites are generally less than half an inch in length, and their wings will be opaque and milky in color. An ant’s wings are transparent, with dark veins obvious.
The Complete Book of Home Inspection by Norman Becker
Termites and Borers: A Homeowner’s Guide by Phillip Hadlington and Christine Marsden