THE WKSTERN PINE-DESTROYING BARKREETLE. 29 



which must occur in large numbers before they can attack and kill a 

 tree. Some of the living trees in the immediate neighborhood of the 

 trap trees may be attacked by beetles attracted to the vicinity by the 

 felled or girdled trees. These should be felled and treated tiie same 

 as trap trees. 



If the conditions appear to warrant it, additional trees should be 

 girdled or felled about the first part of August to catch the second 

 brood. These may be barked, to kill the broods, any time between 

 the first part of October and the first part of the following May. 



StrMMABY. 

 HABITS AND LIFE HISTORY. 



The western pine-destroying barkbeetle usually attacks and kills 

 the best examples of western yellow pine and sugar pine. 



If neglected and under certain conditions favorable to the species, 

 it is capable of devastating the pine forests over large areas. The 

 broods of the beetle pass the winter in the outer bark of trees killed 

 by it the previous summer. The adults of the overwintering broods 

 emerge and fly in ^Maj-, June, and July, the beginning and ending of 

 the period varying with the seasons, latitude, and altitude. 



The first eggs from the first generation are deposited in June or 

 July, and in some of the warm localities possibly as early as the middle 

 of May. In localities intermediate between the colder and wanner 

 regions the majority of the adults of the first generation evidently 

 develop and emerge in August, but some individuals may remain in 

 the trees until June of the next year. 



The first eggs of the second generation are evidently deposited in 

 August and September, depending on locality, and it would appear 

 that in intermediate localises all of the broods of this generation pass 

 the winter (hibernate) in the larval stage in the outer bark. In the 

 warmer localities some of them may develop and emerge in the fall, 

 \vliile in the colder localities there may be but one generation. 



The first evidence of attack on living trees is the presence of pitch 

 tubes (figs. 11 and 12, c) on the bark or of reddish borings lodged in 

 the crevices and around the base of the tree. 



During the fall, winter, and following spring, after a successful 

 attack, the infested trees will be indicated by the fading yellowish 

 and reddish leaves. 



The work of the insect will be indicated by the winding galleries 

 through the inner bark (fig. 8). Trees from which the broods have 

 emerged will be indicated by large numbers of small holes through the 

 outer bark (fig. 12). 



REMEDIES. 



The principal areas of infestation and the principal patches of 

 infested trees should be located in September and October. 



