DESTRUCTIVE ANIMALS, BIRDS, INSECTS 113 



largely reduced by a careful attention to the following general 

 rules, the great thing being to keep the woods in a clean, 

 healthy condition. 



1. Careful choice of species to suit soil and climate. 



2. Formation of mixed woods, more especially mixing 

 broad -leaved trees with conifers. Pure woods on a large 

 scale are especially susceptible to insect attacks. 



3. Early and frequent thinnings should be made to remove 

 all dead and dying trees. 



4. Careful preservation of the fertility of the soil, by mixing 

 soil-improving trees with light-demanders. 



5. Removal of all trees broken by wind or injured by fire. 



6. Avoidance of large felling areas in one place. It is, for 

 instance, better to cut ten acres in one part, and ten acres in 

 another part of the forest, than to clear twenty acres in one 

 spot. Moreover, a cutting should not be made adjoining 

 a previous one till the young trees on the latter are well 

 established ; this is specially important in conifer woods. 



7. All material felled should be rapidly removed from the 

 wood, and should not be left lying about. 



8. All insectivorous birds should be protected and en- 

 couraged. These are included in the list already given, under 

 the headings 3 and 4. 



To encourage birds a few hollow trees and clumps of under- 

 wood should be left standing in the woods, here and there, 

 to provide nesting-places. 



Toads and frogs are useful in nurseries, and spiders are 

 great destroyers of insects. 



With regard to remedial measures, it is unfortunately very 

 difficult to take steps against most species, owing to the heavy 

 expense of doing things on a large scale. In orchards and 

 in small plantations remedial measures will often be successful, 

 but in a large forest it is seldom possible to fight effectively 

 against these pests. The following measures may be tried 

 in certain cases : 



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