Discovering winged termites indoors almost always indicates an infestation warranting treatment. Since the swarmers are attracted to light, they often are seen around windows and doors. People often confuse winged termites with ants, which tend to swarm at the same time of year. Termites have straight antennae, a uniformly thickened waist, and wings of equal size. Conversely, ants have elbowed antennae, constricted waists, and forewings that are longer than the hind wings.
Swarms of termites emerging from tree stumps, woodpiles, etc. out in the yard are not necessarily cause for concern, and do not automatically mean the house is infested. On the other hand, if swarmers are emerging next to the foundation or from abutting porches or patios, there's a good chance the home is infested as well.
Other signs of infestation are earthen “mud” tubes extending over foundation walls, support piers, sill plates, floor joists, etc.The mud tubes are typically about the diameter of a pencil, but sometimes can be thicker. Termites construct the tubes for shelter as they travel between their underground colonies and the structure. To help determine if an infestation is active, the tubes may be broken open and checked for the presence of small, creamy-white worker termites. If a tube happens to be vacant, it does not necessarily mean that the infestation is inactive; termites often abandon sections of tube while foraging elsewhere in the structure.
Termite-damaged wood is hollowed out along the grain, with bits of dried mud or soil lining the feeding galleries. Wood damaged by moisture or other types of insects (e.g., carpenter ants) will not have this appearance. Occasionally termites also bore tiny holes through drywall or plaster, accompanied by bits of soil around the margin. Rippled or sunken traces behind wall coverings can also be indicative of termites tunneling underneath.
Oftentimes there will be no clear indication of infestation. Termites are cryptic creatures and infestations can go undetected for years, hidden behind walls, floor coverings, insulation, and other obstructions. Termite feeding and damage can even progress undetected in exposed wood because the outer surface usually remains intact. Confirmation of termites often requires the keen eye of a professional -- however, even the most experienced inspector can overlook signs that are hidden.