SUBTERRANEAN TERMITES

A, Section through foundation, floor, and wall of house and a, , concrete slab porch with no termite protection; b, shelter tubes on basement wall. The red lines indicate common ,sources and routes of infestation. (Note wood scraps in backfill.) B, Some castes of f termites; c, soldier; d, winged reproductive form; and e, worker (all greatly enlarged).

SUBTERRANEAN TERMITES

Subterranean termites can cause extensive damage to the woodwork and other cellulose-containing products stored in buildings or used in the construction of buildings.

Usually they get the water they need to live from the soil where their colony is established. Their food they get from wood. A termite colony comprises winged reproductive adults, mature workers, soldiers, and young nymphs. Each has specific duties to perform.

Winged adults often emerge in the early spring. They fly away to establish new colonies or else shed their wings and die if they cannot find their way back to the ground. This kind of termite cannot become established in the seasoned woodwork or furniture in a building. It dies if it cannot get to moisture. There is only one flight each year from a particular colony.

The workers do the damage to wood. They excavate it, making channels that run parallel with the grain. The sides of the galleries are stained with grayish excrement, which is characteristic only of termites. Their galleries are free of powdered wood dust. This distinguishes their work from that of powder-post beetles, whose feeding tunnels are filled with it. Termites occur in every State but are more prevalent in the southern half of the country.

Control: One can control subterranean termites by blocking them off from soil. To do that, foundations must be made impervious to their attack; masonry walls must be free of voids; and expansion joints must be filled with coal-tar pitch. The sub-floor space of unexcavated buildings must have proper clearance (18 inches from soil to wood), adequate ventilation, and drainage. If wood supports are necessary, they must rest on poured concrete bases at least 6 inches above the ground level. Enclosed porches should have access panels to permit periodic inspections and chemical treatments if necessary. After such structural modifications are made as are necessary to block the entry of termites, the soil next to foundation walls and piers must be poisoned to kill termites already present in it and to set up a toxic barrier to prevent others from entering.

Trenches for holding soil poisons must be dug 1 foot wide and 15 inches deep along the foundations of buildings having shallow footings and no basements. The trenches should be dug twice as deep along foundation walls of buildings having full basements and deep footings. Soil poisons generally are applied at the rate of one-half gallon per lineal foot in the shallow trench and at twice that rate in the deeper one. They are applied by mixing them with the soil as it is replaced in the trench.

These chemical mixtures are effective: 10-percent solution of sodium arsenite; 5-percent solution of DDT in No. 2 fuel oil; 5-percent solution of pentachlorophenol in fuel oil; one part orthodichlorobenzene diluted with 3 parts of fuel oil; one part trichlorobenzene diluted with 3 parts of fuel oil; one part coal-tar creosote diluted with 2 parts of fuel oil. All those mixtures are poisonous.