PERIOD OF FELLING BAMBOOS. 83 



Turning to another point in Mr. Stebbing's paper there seenivS 

 to be considerable doubt as to which explanation of the rela- 

 tion between the sap and the beetles is correct. Two are 

 given : — 



(1) That an abundance of sap hinders the beetles tn their 



boring and tends to drown them out. 



(2) That the beetles feed on the sap and therefore attack 



more readily when abundance of sap provides a 

 good supply of food. 



It will be seen that the two explanations are contradictory 

 and cannot both be true. The former falls into line with the 

 efficacy of soaking the bamboos in water. There seems to be 

 good evidence that this precaution is of considerable value. 

 If my explanation of the effect of cutting on dark as contrasted 

 with moonhght nights be true, then they also would fall into 

 line with this idea. For when the bamboos are felled on dark 

 nights they are full of what is largely pure water containing 

 certain salts, and the sap present is much more watery than 

 when the bamboo culm is drier during the daJ^ Thus any 

 effect of this sort would be explained on the drowning out 

 theory. When we distinguished between an abundance of sap 

 and an abundance of food material in the sap, we may get the 

 above effect also explained on the second theory, for though 

 sap is more abundant on dark nights and it might seem that 

 food for the attacking beetles would be more abundant, yet 

 it must be remembered that the sap is more dilute on dark 

 nights, and though more abiuidant may possibly contain less 

 organic food for the insects. Thus the comparative immunity 

 may be due to the fact that not only does the large amount of 

 sap tend to hinder the beetles hi burrowing, but also the food 

 supply in the sap may be smaller as it is more dilute. 



I cannot give any reconcihation between this view and that 

 which supposes that when the moon is full the bamboos contain 

 more sap and therefore that time should be avoided for felling, 

 since the fermenting sap forms an attractive food supply for 

 the beetles. In the few cases in which we have definite facts 

 to go upon the bamboos seem more immune from attack when 

 felled full of sap, and for this fact certain explanations can be 

 put forward, as indicated above. It is quite likely therefore 



