Termites

The subterranean termite Reticulitermis flavipes (Kollar) is probably the most destructive and widely distributed species in North America. This species has acclimatized to southern Ontario to such a degree that 27 municipalities report some degree of infestation.

Subterranean termites were first reported in Ontario at Point Pelee in 1929. It has subsequently been reported in Toronto (1938), Windsor (1950), Kincardine (1954), Oxley (1955), Amherstburg and Dresden (1968) and Guelph (1975). Presently in Metropolitan Toronto, the termite infested area extends through a radius of approximately 30 kilometers.

In contrast to termites, carpenter ants do not eat wood and other cellulose-based materials, but instead simply excavate living quarters and hatching chambers that are usually quite limited in extent.

Powder post beetles only do significant damage when multiple generations continually re-infest the same piece of wood. Also, powder post beetle damage is restricted to hardwoods, and since most structural framing is made of softwood lumber it is rarely attacked by these insects.

Carpenter ants, found in the Pacific Northwest, the northern Midwest, New England and southern Canada, are distinguishable from termites by their dark colour, narrow waists, elbowed antennae and when present, the large front and small rear wings. Carpenter ants rarely attack sound dry wood, preferring damp wood, foam or cellulose insulation, and do not use wood for food. They are more easily spotted than termites as they expel wood fragments from their excavations, and forage for food in the open. The presence of carpenter ants may indicate moisture problems in the building as they generally prefer already rotting wood.

Several species of powder post beetles are to be found in the U.S. and Canada. They vary in length from 1/16″ to 3/8″, but generally have flattened bodies, a prominent head and segmented antennae. True powder post beetles attack only hardwoods (particularly oak, hickory, ash, walnut and cherry) but other species of wood boring beetles attack both hardwoods and softwoods.

Powder post beetle larvae cause millions of dollars worth of damage in the US and Canada annually, and are almost as destructive as termites. Adult beetles lay their eggs in the surface pores of wood. The larvae bore into the wood as soon as they hatch. Living in the wood, they create tunnels called galleries as they eat their way through the timbers. When the larvae are nearly full grown, they bore near to the surface of the wood and pupate. The adults bore out through the surface soon after pupation, pushing a fine powdery wood dust, usually a copper to yellow-gold in color, out of the wood as they emerge.

Termite Characteristics:

Subterranean termites are social insects, feeding on cellulose and living in colonies in the soil. These colonies are close to moisture, and can be readily relocated due to temperature or other environmental changes. Termites travel through soil, in wood itself, or through shelter tubes.

In the termite colony there are generally several generations present. The colony is made up of several castes (forms) (larvae, nymphs, secondary and primary reproductives, soldiers and workers), who carry out specific duties or functions.

The female reproductives may thousands of eggs. These eggs hatch and pass through an immature stage (larvae) before finally differentiating into either a worker, soldier or reproductive caste.

The primary female reproductive (the queen), is very rarely found in Ontario, whereas secondary reproductives in the colony carry on extensive reproduction.

The two wingless non-reproductive castes consist of the soldiers and workers. The soldiers defend the colony from outside attack, while the workers carry out all duties except defence and reproduction. For example, the workers feed the reproductives, larvae and soldiers, care for the eggs, and construct tunnels and shelter tubes. The soldier caste consists of sterile adults with large heads and pincher-like mouth parts. These soldiers make up 2-3 % of the total colony.

There are three known methods by which a new termite colony may be established.

The first method, common in the warmer climates of the southern United States, is called swarming. This occurs usually in spring, when large numbers of winged primary reproductives (alates) (top photo) emerge from a colony, fly a very short distance, mate and then establish a new colony. Although alates are found in Ontario, rarely do they swarm.

The second method is called “budding”. In this method, when a colony becomes sufficiently large, or a portion of a colony becomes separated from the main colony, new secondary reproductives are formed from larvae or nymphs and the nucleus of a new colony is established.

The third method of dispersal is through infested wood or soil being transported to a new location. As few as 15-40 larvae or nymphs contained in the infested material may moult to become secondary reproductives and begin a new colony.

The worker termites are white in colour and approximately 6mm (1/4 inch) in length. Their  消滅白蟻 antennae are straight (not elbowed) and the body is not narrowed at the waist, which distinguish them from ants. They have chewing mouth parts and are responsible for foraging and feeding the dependent members of the colony. The hind gut of the worker contains protozoa (single-celled animals) which assist in breaking down cellulose into its component parts which are digestible by the termite. The worker termite causes the structural damages.

Soldier termites are similar in size and colour to workers, but have an enlarged brownish coloured head with large modified mandibles (large biting jaws), used for defense.

Termites have a very thin cuticle (skin) and are subject to rapid desiccation (drying out) if exposed to the environment outside their enclosed habitat. In order to maintain a highly controlled environment, termites must live in a closed system. Colonies in wood are always contained within an outside shell of cellulose material. In this way, they are protected from exposure to the outside.

Often shelter tubesconstructed of soil particles cemented together by excrement or secretions from the mouth are used to connect the outside soil to a building and for crossing a concrete or metallic portion in a structure. The presence of a shelter tube is generally the first physical evidence of a termite infestation.

Damage to Wood:

The subterranean termite is very closely associated with the soil, which is its main source of life-sustaining moisture. Termite food consists of cellulose obtained from wood and wood products. Decaying damp wood is preferred but termites are also able to feed on sound, dry lumber.

The series of galleries (area hollowed out) created by termites in wood give a honeycomb appearance. These galleries follow the wood grain. Interior galleries contain greyish specks of excrement and earth, called frass.

The damage to wood is usually not noticeable on the surface, as the termite avoids exposure to air. Therefore the exterior surface of the wood must be stripped away to see the damage.. Termites do not reduce wood to a powdery mass, or push wood particles to the outside as do some wood-boring insects, such as carpenter ants and powder post beetles.

Evidence of an Infestation:

The presence of shelter tubes over the surface of foundation walls is the primary sign of a termite infestation. These tubes are 6mm (1/4 inch) to 12mm (1/2 inch) wide, and can extend many centimetres in length until wood is discovered. These tubes protect termites form the drying effect of air, and maintain the termites’ contact with the soil.

 

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