PREVENTIVE RULES. 165 



Even on sandy soils, where Scots pine naturally thrives, 

 a mixture of Weymouth pine should be introduced, and a 

 few birch, aspen and robinia. If the pines should be killed 

 outright by insects, the wood will not become absolutely 

 bare. 



(iii) Careful and frequent examination of the woods for 

 injurious insects. This precaution is most important in coni- 

 ferous woods on poor, dry soil, in warm localities and 

 especially during the spring. 



It is most important to keep a careful watch round places 

 where swarms of insects exist, and from which damage gene- 

 rally extends in all directions. The subordinate Forest Staff 

 must be instructed to recognise and attend to the signs of an 

 impending attack of this kind. Such signs are: unusual num- 

 bers of woodpeckers or cuckoos in a compartment; bitten-off 

 leaves or needles lying on the ground ; spun threads hanging 

 from the twigs ; withering of foliage : excrement, or boring 

 refuse, or bore-holes in the stems ; exudation of resin ; dis- 

 coloration or peeling off of bark ; and appearance of numbers 

 of ichneumon-wasps or flies, etc. 



(iv) Early and frequent thinnings, without interruption of 

 the leaf canopy, are desirable. Such thinnings should remove 

 all forest growth in a suppressed, sickly, or even suspicious 

 condition. A forester who merely removes dead wood does 

 nothing to prevent insect attacks, for in it only unimportant 

 species breed. Dying stems are the favourite resort of 

 bark-beetles. 



(v) Every attention should be paid to the rules for main- 

 taining and improving the quality of the soil. This is best 

 accomplished by careful preservation of the soil-covering, by 

 draining away any superfluity of moisture, and by timely 

 under-planting woods of light-demanding trees, such as 

 oak, larch or Scots pine, with shadebearing ones, beech, 

 silver-fir, etc. 



(vi) Suitable preventive measures must be taken against 

 damage by wind, frost, snow, ice, fire or insects. Broken wood 

 must be worked up and removed from the forest as soon as 

 possible, or at least barked. 



(vii) In the clear-cutting system, avoid large felling areas, so 



