76 INSECTS INJUBIOUS TO FORESTS. 
beehives and tree boxes; wooden electrotype blocks, and books (PL 
IV) and documents stored in damp, dark places, etc. ; timber in con- 
tact with the ground being especially liable to serious damage. Often 
the damaged material has to be removed and replaced, or rebuilt. 
The wood of no species of native tree of commercial importance is 
"immune" to attack, although some are relatively more resistant 
than others. Such damage has occurred as far north as Boston and 
the shores of the Great Lakes, but greatly increases as the Tropics are 
approached. In the Southern States termites are especially destruc- 
tive to wooden underpinning, beams, and flooring (PI. XVII, fig. 2), 
and all other material of wood accessible in buildings. They enter 
buildings by means of tunnels through the ground, by way of wooden 
joists, or by means of covered paths (minute "sheds" constructed of 
earth and excrement of the superficial consistency of sand), leading to 
the woodwork over the surface foundations of stone or other material 
which they can not penetrate. This enables them to avoid the light. 
Thus termites silently, secretly, and ceaselessly work their insidious 
damage, instinctively never perforating the exposed surface of timber, 
except to enable the sexed adults to swarm. Sometimes the emerg- 
ence of these winged forms is the first indication of their presence, 
but at other times joists and floors collapse without warning. 
PREVENTIVES, REMEDIES, AND ''IMMUNE" WOODS. 
Forest products in contact with the ground should be impregnated 
with coal-tar creosote, which is a permanent preventive against 
attack by our native termites. Coal-tar creosote has many prop- 
erties which would recommend its use in this respect, for it is also a 
fungicide, and, being insoluble in water, will not leach out in wet 
locations. These requirements furnish objections to many chem- 
icals that otherwise are very effective insecticides. The various 
methods of superficially treating timber, as by charring, by brushing, 
or by dipping with various chemical preservatives, among which are 
creosotes, carbolineums, etc., have proven to be temporarily effec- 
tive iii preventing attack, if the work is thoroughly done. If not 
thoroughly done, termites enter through the untreated or imper- 
fectly treated portions, especially through weathering checks and 
knots. Where the bases of poles, mine props, etc., are left untreated 
termites enter the timber from below, and, avoiding the treated 
portions, come up through the interior. Charred timber is effective 
against termite attack for a period less than a year, although it is not 
seriously damaged at the end of one year. It will readily be 
seen that neither brushing nor spraying the exterior after place- 
a Snyder, T. E. Insects injurious to forests and forest products. Damage to chest- 
nut telephone and telegraph poles by wood-boring insects. IT. S. Dept. Agr., Bur. 
Ent., Bui. 94, pt. 1. pp. 12, figs. 3, pis. 2, Dec. 31, 1910. See p. 9-10. 
