41 



fell were attacked by large numbers of Dendroctonus, thereby fur- 

 nishing- good evidence that between these dates was the proper period 

 (spring of 1900) to girdle the trees to attract the insects. 



Of the twenty-five trees girdled on the other dates — May 29, June 

 19, July 11, and September 1 — only seven were attacked by sufficient 

 numbers to kill the trees. 



These results, together with observations hj the author during the 

 investigations on the dates of the appearance of the leaves and flowers 

 on different) trees, indicate that the best period to girdle spruce trees 

 to attract the spruce-destroying beetle away from other trees may 

 vary with the seasons, but will be about ten days, commencing 

 when the catkins (flower stems) are falling from the birches, and con- 

 tinuing while the fire cherry and the hobble bush are in flower. 

 Another good guide will be to commence when the first pupa3 of the 

 destructive beetle commence to appear in the bark and continue until 

 the beetles commence to fly. 



SUGGESTIONS AND RECOMMENDATIONS. 



The prime objects of the investigation were not only to determine 

 facts relating to the causes of the death of the spruce, but to obtain 

 evidence on which to base suggestions and recommendations for 

 mitigating or controlling the ravages of the spruce-destroying beetle; 

 preventing the total loss of the vast amount of timber already killed, 

 and for reducing or preventing the losses from its ravages in the 

 future. 



It has seemed a hopeless undertaking to determine practical 

 methods of combating invasions of destructive insects in a vast 

 wilderness of virgin forest, or to accomplish much toward prevent- 

 ing total loss. of the millions of feet of timber killed or injured b} T 

 them, especially in a country like ours, where improved forestry is in 

 its infancy. But with a knowledge of the principal depredator, its 

 habits, its life history, its enemies, and the conditions, favorable or 

 unfavorable, for its destructive work, facts have been determined on 

 which to base conclusions relating to simple, inexpensive, and prac- 

 tical methods of combating the insects and preventing a large part of 

 the losses. 



It then rests with the owner of the property to study the practical 

 features of the ijroblem and the facts determined by the investigator, 

 in order that he may intelligently apply the recommendations to the 

 varying needs and conditions as in each case seems most advisable. 

 It should be remembered that it is the investigator's mission to deter- 

 mine the facts and evidences, and present them with recommenda- 

 tions and suggestions, while the owner of the damaged or threatened 

 property must study and utilize or discard them, as his practi- 

 cal judgment and business interests may indicate is best in each 

 particular case. 



