Subterranean Termites


Subterranean termites are social insects that live in colonies within the ground and have specialized castes to perform specific colony functions. The termite colony has three primary castes: workers, soldiers, and the reproductives (kings, queens, and secondaries). The creamy-white workers (Fig. 3) are seldom seen unless a termite tube or infested wood is broken open. It is the workers that feed on the wood and cause damage. Individual workers are believed to survive for up to five years. Soldiers have elongated yellowish heads with large jaws and are about the same size as the adult worker-a quarter-inch (Figure 4). There are fewer soldiers than their associated workers, and must rely on the workers to feed them. Whenever the colony is invaded or a hole is made in a tube or piece of infested wood, the soldiers will use their jaws to defend the breach. The secondaries are supplementary reproductive females that occur in mature colonies under favorable conditions. The kings and queens (Figure 5) are dark-brown or black and about 3/8 to 1/2 inch long. They have two pairs of translucent wings of equal length, which break off shortly after swarming. Very often the shed wings are the only evidence that termites are in a building. In Pennsylvania, swarms of winged termites usually emerge between February and June.

Life History

During late winter or early spring, swarms of the reproductive caste may be noticed in infested buildings. These black, winged termites are the stage most commonly seen, since the other castes do not willingly expose themselves to light. Winged termites are attracted to light, and when they emerge within buildings, they swarm about doors and windows. After crawling or fluttering about for a short time, the termites break off their wings and locate a mate. Each pair attempts to locate moist wood in contact with the soil to start a new colony, but few succeed. Although they alarm the homeowner and can be a nuisance, no damage is done by the winged forms.

How to Recognize Termites and Termite Damage

The presence of swarming termites or their wings alone is a sure sign that termites are working in a building. Winged termites are often confused with winged ants. Most species of ants in the house are only nuisances and, except for carpenter ants, do not damage wood. For this reason it is necessary to know the differences between winged termites and winged ants. The easiest way to distinguish the two groups is to look at their waists. An ant has a narrow, wasp-like waist; a termite has a broad waist. The antennae or feelers of ants are L-shaped, whereas those of termites are straight. Furthermore, the four wings of termites are of equal length and nearly twice as long as the termite body, while ant wings are approximately equal to the length of the ant, and the fore and hind wings are of unequal length.

Wood attacked by termites has runways or passages that are coated with an earth-like material glued to the wood. Where the wood has been infested for some time, it may be largely hollowed out with passages and may be rotten in appearance (Fig. 6 & 7). Upon probing such wood with a screwdriver or similar tool, many of the hidden worker termites may spill out.

Another sign of termites in the house is the presence of termite tubes (Figure 8). Termites make these earth-colored tubes for a number of reasons, primarily as a protected runway from the earth to the wood they feed on. Moreover, these tubes may serve as swarming exits for the winged termites. Look for these tubes on the cellar walls, on wooden posts, wall studs, mudsills, and door and window trim. Wood embedded in earth or in concrete cellar floors is especially susceptible to termites.

Where Are Some of the Places You Should Look If You Believe You Have Termites?

Wooden posts, steps, door frames, and trim embedded in an earth or concrete floor are especially susceptible to termite infestation. Wood siding, window frames, steps, and similar materials covered by earth or resting on the ground may also be attacked by termites. Where the termite infestation is extensive, the flooring and framework in the walls can be damaged by termites; this is often the case where houses are built on concrete slabs. Termites especially favor areas around furnaces, chimneys, hot water heaters, and hot water pipes that provide warmth during cold months.

The extent of damage to structural timbers and woodwork can be determined by a careful inspection of the building. Although you may choose to make the inspection yourself, we recommend you have a professional pest control operator inspect the building. Licensed pest control companies have individuals with experience in detecting termite infestations that many laypeople would otherwise overlook.

All woodwork in suspect areas should be probed for soundness and visually inspected for any sign of mud tunnels. An awl, ice pick, screwdriver, or similar instrument is commonly used to probe the wood. After the area and extent of infestation are determined, control measures can be planned.

Termite Bait Treatment

Termite Baits - In recent years, termite baits have gained in popularity. This alternative to liquid barrier treatments is a welcome addition and will assist in the battle against termite infestations. Baiting involves the use of an attractant (wood stakes, cardboard, or other cellulose-based material) to establish termite feeding. The active ingredient (insecticide) is either added after feeding begins, or may be included in the initial baiting. Termites feeding on the treated material will carry the toxicant back to the colony where it adversely affects the colony, possibly eliminating the entire colony.

Baits are especially important in treating structures with wells or springs close to the foundation; drainage tiles around the foundation; air ducts under or imbedded in the slab; or in situations where a perennial high water table makes conventional soil treatment ill advised. Although data suggest they may be valuable as a stand-alone treatment, many of the factors that affect baiting efficacy are poorly understood. As with soil application of termiticides, it is recommended that licensed, experienced pest control companies be hired to provide a baiting service. Baiting, in conjunction with a partial (or complete) soil treatment may be advisable. The USDA-FS does not perform efficacy tests on termite baits.

Termite Swarm Facts

Just as we are ready to enjoy spring, termites are beginning to swarm in full swing.
Subterranean termites live in colonies underground to avoid sunshine and outside air. Termite swarmers are the reproductive form from mature colonies. These are the only type that most people ever see. It takes a number of years for a termite colony to develop into maturity.
Swarming is usually the first time a homeowner becomes aware of a termite problem. If swarming is found inside, you have a termite infestation somewhere in your house. Swarmers come out of cracks, crevices, or small holes in wall, attic, window and door frames, and similar gaps. They are often accompanied by mud marks (Photo 1). In this case, you need to contact your termite protection contract provider or call reputable pest control professional for a thorough inspection and treatment.

If swarming occurs around houses outside, you may have termite colonies infesting trees, tree stumps, fence, poles or wooden structures in the yard. Do not panic, but it is wise to locate the infested areas and do a targeted treatment.
You should understand that the absence of typical swarming signs does not mean there is no termite activity happening below the surface of a home.
Swarmers have short lifespans. An overwhelming majority of the swarmers will die (photo 2) if they are able to find somewhere they can burrow in or somewhere that is constantly moist and has wood. Such locations occur outside in woody ground or occasionally in a leaking attic or roof.

What termite species are there swarming? If the swarming occurs during the day around noon, it is a native subterranean termite species, which start swarming in early spring. If the swarming occurs in the evening after sunset, it is Formosan subterranean termite, which swarms from May through June.
Preventive options for homeowners:
1) Remove stumps, scrap wood, grade stakes, foam boards, cardboard boxes and newspapers from around structures.
2) Move firewood, landscape timbers and compost piles away from foundations.
3) Eliminate moisture around foundations. Divert water from the house by grading the soil and installing gutters.
4) Cut back shrubs, vines, tall grasses and other dense vegetation growing against structures.
5) Do not let mulch to contact wood siding or framing of the doors and windows around the structure.
6) Seal cracks and holes to prevent termite entry.
7) Most importantly, have your home inspected by a licensed pest professional who specializes in termite control.