. 

 against infestation, or be left as trap trees and the baric 



destroyed when it becomes infested. Infested bark must be 

 entirely destroyed. 



"Spotting" . 



"Spotting" is the work of locating infested trees. 

 The chief of party should do all the spotting. The best 

 method has proved to be by snail watersheds, covering the 

 area by contours of varying distances, according to the den- 

 sity of the timber; or where the watershed is small and the 

 ridges low, spotting one side of the stream or gulch first, 

 following up with the remaining aide. The location of in- 

 fested trees may often be determined by using field glasses. . 

 Glasses are also useful in looking for pitch tubes where there 

 is no evidence of bark-borers on the base of the tree. Of 

 coTirse, a uniform yellowing of the foliage is always a reason- 

 ably sure sign of infestation somewhere on the tree, whether 

 there is any other visible evidence or not. 



Various theories have been put forward, regarding 

 the length of flight of the different species of lendroctonus 

 and Ips. At present there is no very definite data. One 

 thing, however, seems moderately certain. The various spe- 

 cies of bark beetles do not fly any great distance, if trees 

 of the particular species required by them are nearby. 



