xv. 4 Oshima: Formosan Termites SS7 



Damage to brick walls. — There are several records in For- 

 mosa of modern brick building's having been infested by 

 Coptotermes formosanus. It is absolutely impossible for it to 

 attack brick itself; but, according to my actual observation, 

 the mortar which is used as a cementing material for bricks 

 is subject to attack. 



In building a thick brick wall the following method is adopted : 

 The face bricks are laid upon a bed of mortar; the mortar, 

 in a semifluid condition, is then poured into the space between 

 the face bricks ; the bricks are then pushed rapidly, horizontally 

 for a short distance, into their position; a certain amount of 

 the mortar is thus displaced; this rises in the side joints and 

 completely fills all the interstices; should the mortar not rise 

 to the top of the joints, the vacant spaces are filled up, when the 

 next course is larried. 



All the interstices between the bricks would be completely 

 filled, if the bedding could be carried on theoretically; but this 

 is practically impossible, so that there are almost sure to be 

 voids in brick walls. Under such conditions, termites prefer to 

 pass through brick walls, if they have a chance to permeate 

 them, rather than to excavate ordinary walls; because the voids 

 are always in a favorable condition for their life, being pro- 

 tected from the sunlight and containing a proper amount of 

 moisture. 



There are two kinds of mortar used for constructional work; 

 namely, cement mortar and lime mortar. The former is com- 

 posed of sand and Portland cement (the ratio of Portland 

 cement to sand is from one to two to one to four), while the 

 latter is composed of moderately hydraulic lime and sand (the 

 ratio of lime to sand is usually one to two). 



In Formosa until a comparatively recent date lime mortar was 

 exclusively used for the bedding of bricks. It has been found, 

 however, that Coptotermes formosanus easily penetrates brick 

 buildings and causes serious damage (Plate VII). Since the 

 Government has required the use of cement mortar instead of 

 lime mortar there has been no record of damage to brick walls. 

 Therefore, it seems reasonable to conclude that there exists 

 some special relationship between lime and the destructive power 

 of Coptotermes formosanus. 



The soldier of Coptotermes formosanus is provided with a 

 special gland on the forehead, which secretes a milky, acidulous 

 fluid; its excreta and saliva are also acidulous, while those 

 of the worker are alkaline. In the passages perforating the lime 



