xv, 4 Oshima: Formosan Termites 347 



new colony, raising a number of workers and soldiers. It is 

 possible, therefore, that in the case of a building infested by 

 the winged forms, the damage may be extended year after year, 

 in spite of the existence of the termite-proof concrete layer. 



The office of the Nippon Yusen Kaisha at Keelung, Formosa, 

 which was built in 1915 (Plate X, fig. 1), is said to be a good 

 example of the termite-proof construction. Nevertheless, in 

 August, 1916, that is, only one year later, damage caused by 

 termites was found on the second floor (Plate X, fig. 2). At 

 that time there was no damage on the first floor; there was no 

 connection between the nests constructed on the second floor and 

 the ground; the concrete layer on the ground level was perfect, 

 having neither crack nor joint; many hyaline wings, which had 

 been cast by the imagoes of Coptotermes formosanus, were found 

 in the building; couples accompanied by young larvae were 

 found in the brick walls, especially in wood bricks. Such being 

 the case, there could be no doubt that the building had been 

 infested by the winged form, which entered the house in the 

 swarming season. 



The concrete layer on the ground level may be strong enough 

 to prevent the pest that starts from the ground, but it is of no 

 use in preventing the intrusion of the winged forms. Certainly, 

 in Formosa, the percentage of the damage to buildings has de- 

 creased since the new" method of construction was adopted; but 

 the present building construction is not absolutely termite proof, 

 because it does not prevent the entrance of the winged forms. 



TESTS OF THE RELATIVE RESISTANCE OF NATIVE AND EXOTIC WOODS 



It is evident that the changes made in several parts of build- 

 ings in Formosa are more or less effective in preventing the 

 damage by Coptotermes formosanus; but, since it is almost 

 impossible to prevent the entrance of the winged forms, an 

 investigation to discover other methods of prevention becomes 

 necessary. 



From an economic point of view it is hard to eliminate non- 

 resistant timbers from building materials, especially in the 

 case of Japanese buildings. Under such conditions the treat- 

 ment of timbers so as to provide immunity from the attack of the 

 termite is considered more important than the former method; 

 because it is certain that the preventive measures, namely, con- 

 structing the concrete layer, etc., become unnecessary if the 

 nature of timbers can be so changed that they are absolutely 

 immune from the attack of the termite. 



