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RECOGNIZING THE PRESENCE OF TERMITE INFESTATION IN BUILDINGS
Anti-Termite Construction Measures
Before knowing about measures to Anti-Termite Construction we should know some thing about TERMITES
Termites constitute a separate order of insects called 'Iseptora' ( ises is 'equal' and pteron means 'wing' in Greek). Although, they are commonly called white ants, they are not related to ants. The front pair of wings of the ants'are longer than their hind pair whereas in termites, both pairs are equal. There are over two thousand species of termites of which about 220 are found in India. All these species are not considered to be serious pests.
According to their habits, termites can be divided into two well defined groups:
a) Subterranean or ground nesting termites which build nest. in the soil and live in them, and
b) Non-subterranean or wood nesting termites which live in wood with no contact with soil.
Subterranean termites require moisture to sustain their life. They normally need access to ground at all times. They build tunnels between their nest and source of food through covered runways. These covered tunnels provide humidity conditions thus preventing desiccation and protection against predators, darkness necessary for their movement and for maintaining contact with earth. The subterranean termites enter a building from ground level, under the foundation; working their way upwards through floors, destroying all before them. So little is seen of these termite operations that sometimes the structural member attacked is found to be merely a shell with the inside completely riddled and eaten away.
Non-Subterranean or Drywood Termites The wood nesting species comprise dry wood and dampwood during t termites. Dry wood termites which predominate are able to live even in fairly dry wood and with no contact with soil. These frequently construct ted nests within large dimensional timbers, such as rafters, pests, door and window frames, etc, which they destroy, if not speedily exterminated. However, they are not as prevalent and common as subterranean termites, workers. and are generally confined to coastal regions and interior of eastern India. A termite colony consists of a pair of reproductives, the so-called king and queen and a large number of sterile workers, soldiers, and existing nymphs. If however, the queen is lost or destroyed, her place is taken by a number of supplementary reproductives in some group of termites; thus by removing the queen, the colony will not be destroyed. All the work of , the colony is carried out by the workers. Guarding the colony is the work of the soldiers. The adult workers and soldiers are wingless. The workers are generally grayish white in colour. The soldiers are generally darker than the workers and have a large head and longer mandibles. There are, however, other types of soldiers whose mandibles are small, degenerated and functionless; instead the frontal part of the head is prolonged to form a long nasus; they dispel the enemy by squirting out of white poisonous fluid through the nasus. The reproductivcs, that is, flying adults, have brown or black bodies and are provided with two pairs of long wings of almost equal size in contrast to the reproductives of ants which have two pairs of wings of unequal size.
The food of the termite is cellulosic materials like timber, grass, dead trees, droppings of herbivorous animals, paper, etc. Once termites have found a suitable foot hold in or near a building, they start the. spreading slowly from a central nest -through underground and unnoticed ground galleries in the case of subterranean termites, and galleries within ' to the! the structural member, once they get direct access to them in the case of drywood termites. In their search for food they by pass any obstacle (like concrete or resistant timber to get a suitable food many metres away .
In subterranean termite colony, the workers feed the reproductives, soldiers, winged adults and young nymphs. One of the habits of the termites which is of interest is the trophallaxis by means of which food and other material remain in circulation among different members of the ..colony. Workers are also in the habit of licking the secretions of exudating glands of the physogastric queen.
At certain periods of the year, particularly after a few warm days followed by rain, emergence of winged adults on colonising flights, occurs. This swarming, also called the nuptial flight, may take place any time during the monsoon or post-monsoon period. The flight is short and most of the adults perish due to one reason or the other. The surviving termites soon find their mates, shed their wings and establish a colony if circumstances are favourable. The female of the pair or queen produces a few eggs in the first year. The first batch of the brood comprises only of workers. The rate of reproduction, however, increases rapidly after 2 to 3 years. Although a colony may increase in size comparatively rapidly, very little damage may occur in a period less than 8 to 10 years. Any serious damage may occur in a short time is perhaps due to heavy infestation in the initial stages due to large population of termites existing in the soil before the building is constructed.
RECOGNIZING THE PRESENCE OF TERMITE INFESTATION IN BUILDINGS
Swarms of winged reproductives flying from the soil or wood are the first indication of termite infestation in a building. Often the actual flight may not be observed but the presence of wings discarded by them will be a positive indication of a well established termite colony nearby. Termite damage is not always evident from the exterior in the case of subterranean termites, since they do not reduce wood to a powdery mass or push particles like some of the wood borers or drywood termites. These termites are also recognised by the presence of earth-like shelter tubes which afford them the runways between soil and their food.
Dry wood termites on the contrary may be recognised by their pellets of excreta. Non-subterranean termites excrete pellets of partly digested wood. These may be found in tunnels or on the floor underneath the member which they have attacked. These termites may further be noticed by blisters on wood surfaces due to their forming chambers close .to the surface by eating away the wood and leaving only a thin film of wood on the surface. Also the hollow sound on tapping structural timber will indicate their destructive activity inside.
Anti-Termite Construction Measures
There should be no way i.e crack or wide joint from where the Subterranean termites can find their way to structural wood above the ground level. The fig is illustrative enough to explain there should be no crack or joint between wall and floor.
Anti-Termite Construction Measures
(Non-Subterranean termites)
Since these termites lives in combatively Drywood and does not depend on ground link the above given method of construction hardly have any effect on such termites. so the best method is to use the treated wood or use insecticides spray and injection as the guidelines of manufactures of such insecticides.