BIOLOGY OF THE TERMITES OF THE EASTERN UNITED STATES. 79 
The wood-pulp products and various patented " composition 
boards" used as substitutes for lath, etc., might be made termite proof 
by adding during their manufacture such poisons as white arsenic, 
antimony, bichlorid of mercury, zinc chlorid, etc; tests are being con- 
ducted. 
In general, serious damage by termites to the wood of fire or 
insect killed, standing, merchantable timber can be prevented if the 
timber is utilized within from one to two years from the time that it 
was killed, depending on the species of wood and the locality — one 
year for pine (less in the Southern States) and two years for chestnut. 
Forest tree nursery stock should be planted in ground that has 
been plowed deep late in the fall of the year in a region where injury 
by termites is common. 
Marlatt a states regarding white-ant infestation in buildings that 
setting foundation beams or joists in concrete is only a partial 
protection, since in the settling of the house the concrete will crack 
and afford entrance to the insects. Some protection is afforded by 
removing decaying stumps or posts, etc., adjacent to buildings, by 
drenching infested timbers with kerosene, and by removing infested 
joists in cellars and drenching the ground where they were set with 
kerosene (or carbon bisulphid). Where the injury is confined to 
exposed woodwork in buildings, hydrocyanic-acid gas fumigation b 
is to be recommended, the infested beams and joists beneath being 
exposed, if possible, by opening up the floors. 
Certain species of wood appear to be naturally highly resistant to 
termite attack. Species of wood that, so far as determined by test, c 
have been resistant to attack by our native termites are all tropical 
species and woods too expensive for ordinary use, including teak 
(Tectonia grandis) from Siam and Burma, greenheart (Nectandra 
rodisei) d from South America and the West Indies, "peroba" (several 
species of Aspidosperma) from South America, and mahogany 
(Swietenia mahoghani) from tropical America. Hagen 6 states that, 
according to Kirby, " Indian oak" or teak (Tectonia grandis) and 
"ironwood " (Sideroxylon) of India are immune to attack by termites. 
This immunity ( ?) or relative resistance of ironwood is not due to 
hardness, since Asiatic termites attack the hardest wood, Lignum- 
vitse, but to the presence in the wood of substances (as oils or alka- 
« Op. cit. 
& Howard, L. O., and Popenoe, C. H. Hydrocyanic-acid gas against household 
insects. TJ. S. Dept. Agr., Bur. Ent., Circ. 163, p. 8, November 29, 1912. 
c Impregnation of wood to resist insect attack. Amer. Lumberman, no. 2009, p. 32, 
November 15, 1913. 
^This wood has been superficially attacked by termites after 12 months' test; the 
wood was eaten to the depth of one-eighth inch. 
« Hagen, H. A. Monographie der Termiten. Linnsea Entomologica, Bd. 10, p. 
44-45, 1855. 
