21 

 NEED OF FURTHER INVESTIGATION. 



While considerable evidence was found during the time devoted to 

 the investigation, there yet remains much to be determined by detailed 

 study and experiments relating to the peculiar conditions which bring 

 about the invasion of a rare or new insect and the conditions which con- 

 tribute to its rapid multiplication and destructive work, as well as those 

 which contribute to its decline and sudden disappearance. There are 

 also many facts, yet to be determined, relating to the life history and 

 peculiar habits of the pine-destroying beetle and other numerous 

 enemies of the trees, and the natural enemies of such insects. The 

 determination of these facts is very necessary in order to suggest the 

 best methods of preventing losses in the future. It will also help us 

 to utilize nature's methods of protecting such of the species as are of 

 use to man and destroying those that are objectionable. 



Cutting and barking tJie infested trees this winter would be an exper- 

 iment of great importance, not only in its prospects of ending the 

 trouble, but in demonstrating whether or not it is a practicable method 

 to be adopted under similar conditions in the future. It will also be 

 of interest, and probably of considerable economic importance, to note 

 the effect that this process of insect destruction will have on the other 

 injurious and beneficial insects involved. 



The experiments of girdling, cutting, and treating trees with a view 

 of rendering them attractive to the migrating beetles, and thus pro- 

 viding traps for them, is a line of work which should receive special 

 attention next summer. It would serve to demonstrate, or at least 

 indicate, several things which it is quite necessary to know in order 

 to adopt successful methods of preventing future trouble from insect 

 ravages on the pines of this reserve. It would demonstrate whether 

 or not the beetles that emerge from the infested trees which have not 

 been cut and barked could be attracted to trap trees; how and when 

 the rock pine can be girdled or treated to exert the greatest attraction' 

 to the principal enemies, and how the insects thus trapped can be 

 best destroyed. It would also contribute greatly to the study of the 

 life history and habits of the primary and secondary enemies of the 

 trees and the enemies of the insects. 



There are other features relating to the kinds of insects and fungi 

 that attack trees girdled by different methods, or girdled and felled at 

 different times of the year, which should be determined. Indeed, 

 there are many and varied subjects relating to the insects of the rock 

 pine which should be studied during the progress of the present 

 trouble, in order to accumulate data that will be of service in prevent- 

 ing and checking future destructive invasions in the pine forests of the 

 Rocky Mountain region. 



O 



