FOREST PROTECTION 25 



of less importance to the forester than to the pur- 

 chaser of his product. Some of them cause serious 

 losses in lumber yards, ship yards, bark sheds, fac- 

 tories, etc. 



Insects of classes "a" and "b" above are sometimes called 

 "parasitic" because they attack living plants, as distinguished 

 from those of class "c," which feed only on dead timber, and 

 are called "saprophytic." The term "parasite," however, is 

 commonly used in Entomology to denote a species of insect 

 which has another species for its host, and the student should 

 be careful in his reading to distinguish between the broader 

 and narrower uses of the term. 



VIII. PART OF TREE ATTACKED. No part of the tree is entirely 

 free from insect injury. According to species, insects may 

 feed upon the buds (caterpillar causing the fork in the ash), 

 the leaves (elm leaf -beetle), the fruit (chestnut and acorn 

 weevils), the pith (locust shoot-borer), the cambium (larvae 

 of the so-called bark-beetles), the heart- wood (chestnut borers), 

 the sap-wood (many of the longicorn borers), the roots (larvae 

 of May-beetles), and the bark (notably tan-bark). 



IX. DEGREE OF DAMAGE. According to the amount of damage 

 done, insects may be classed as a, Damaging insects; 6, Des- 

 tructive insects, and c, Pernicious insects. Insects are called 

 physiologically obnoxious if they check the growth or propa- 

 gation of plants, and technically obnoxious if they destroy or 

 reduce the technical value without checking the growth. The 

 Hemlock bark-maggot furnishes a good example of the last 

 named class. 



B. REMEDIES AND PREVENTIVES IN GENERAL AGAINST 

 INSECT INJURY. 



I. Select the proper species for reproduction on a given soil. 



II. Encourage mixed forests. 



III. Avoid large continuous clearings. 



IV. Use the ranger staff in controlling the insects. 



V. Remove the weak trees, and strengthen the remaining indi- 

 viduals by means of thinnings. 



VI. Protect and improve the productiveness of the soil. 



VII. Protect the forest from damage by storm, sleet, or fire in the 

 wake of which insect plagues frequently follow. 



