VIII THE SCOLYTID BEETLES. 



Page. 



General methods of control 29 



Habits and seasonal history as suggesting methods of control- - -.^ 29 



Destruction of the broods 30 



Barking the standing trees to kill the broods 30 



Destruction of the broods without removing the hark 30 



Attempts at complete extermination of the beetles unnecessary 31 



Requisites for successful control 31 



How to check and control an extensive invasion 31 



How to control a limited attack 32 



How to maintain control 32 



In State and National forests 32 



In private forests 32 



Inaccessible areas 33 



Trap-tree method of control 33 



Introduction and protection of natural enemies 34 



Importance of systematic forestry 35 



Some results of efforts to control beetle depredations 35 



Detailed information on the species 38 



General explanation of descriptive and other terms 38 



No. 1. The western pine beetle (Dendroctonus hrevicomis Lee.) 42 



Seasonal history 42 



Overwintering stages 42 



Activity of overwintered broods 42 



First generation '. 43 



Second generation 44 



Habits 44 



Economic features 45 



Evidences of attack 45 



Effects on commercial value of the wood 46 



Favorable and unfavorable conditions for the beetle 46 



Methods of control 46 



Basis of information 49 



Bibliography 49 



No. 2. The southwestern pine beetle {Dendroctonus barhen Ilopk.) 49 



Seasonal history 50 



Overwintering stages 50 



Activity of overwintered broods 50 



First generation 50 



Second generation 51 



Economic features and methods of control 51 



Basis of information 52 



Bibliography 50 



No. 3. The roundheaded pine beetle {Dendroctonus convexrifrons Hopk.) 53 



Seasonal history 53 



Overwintering stages 53 



Activity of overwintered broods 53 



Generation 54 



Habits 55 



Economic features 55 



Methods of control 55 



Basis ot information 56 



Bibliography 50 



