354 



In order to determine the relationship between the resistance 

 and the chemical properties of woods, I made the following 

 investigation : 



The quantity of ash and benzene extract in the above-men- 

 tioned woods was measured and compared with the percentage 

 of damage obtained at Tainan. 



Sampling. — A block of wood is cut along the three planes 

 crossed at right angles, and the sawdust is collected. By the 

 diagonal method reduction of the amount of the sample is made 

 repeatedly, until about 20 grams of the sawdust are obtained. 

 This sample is exposed for one hour in an air bath at 105° to 

 110° C. Then it is kept in a desiccator as a representative 

 sample. 



Method of estimation of ash. — A 1-gram sample is heated to 

 redness in a platinum crucible over a Bunsen burner, and the 

 incombustible substances are brought to a constant weight. 



Method of estimation of benzene extract. — To estimate the 

 benzene extract 5.00 grams of the sample are put into a Soxhlet 

 apparatus and extracted with pure benzene for from six to 

 ten hours. The benzene is driven off on a water bath, and 

 afterwards the container is heated in an air bath at 120° C. 

 to a constant weight. All determinations are made in duplicate. 



It is evident that no special relationship exists between the 

 resistance and the amount of ash and benzene extract. It is 

 rather striking, however, that the percentage of benzene extract 

 contained in cypress pine and teak, which are absolutely immune 

 from the attack, is extraordinarily high. 



SUMMARY 



1. In Formosa three species of termite, namely. Lciicotcnnes flaviccps 



Oshima. Coptotcrmcs fonnosanus Shiraki, and Odontotcnncs for- 

 mosanus (Shiraki). are injurious to wooden structures. 



2. A pair of mature individuals of Coptotcrmcs fonnosanus is able to 



start a new colony. 



3. In a newly established colony of Coptotcrmcs formosanus, egg laying 



begins five to thirteen days after swarming. 



4. Coptotcrmcs formosanus lays from one to four eggs a day. 



5. Eggs of Coptotcrmcs formosanus hatch in from twenty- four to 



thirty-two days after they are laid. 



6. The soldier of Coptotcrmcs formosanus develops from the egg laid 



by the queen. 



7. Coptotcrmcs formosanus attacks lime mortar. 



8. The principal food of Coptotcrmcs formosanus is cellulose. 



9. The termite-proof concrete layer is entirely satisfactory in prevent- 



ing the entrance of termites from the ground. 



10. Teak and cypress pine are ahsolutely immune from the attack of 



Formosan termites. 



11. The resistance of timber is not due to its hardness or weight. 



12. The resistance of timber is not due to the inorganic compounds 



contained in it. 



13. The resistance of timber is due to organic compounds that can be 



extracted by benzene or alcolhol. 



14. Cypress pine contains "guajol," a sesquiterpene alcohol. 



