50 



THE SCOLYTID BEETLES. 



SEASONAL HISTORY. 



OVERWINTERING STAGES. 



• The broods pass the winter in all stages from young to matured 

 larvae, young adults, parent adults, and possibly pupae, in the outer 

 bark of trees and logs attacked by the parent beetles the previous 



summer. 



ACTIVITY OF OVERWINTERED BROODS. 



The overwintered parent adults begin to excavate galleries and 

 deposit eggs as soon as warm weather permits in the spring, and con- 

 tinue to do so until about the first of June. The overwintered broods 

 of young adults begin to emerge toward the last of May (northern 

 area) and continue to come out until the last of June or later. The 

 overwintered larvae begin to transform to pupae and adults soon 



Fig. 13.— The southwestern pine beetle: Egg galleries. (Author's illustration.) 



after activity begins in April or May, but retarded individuals may 

 not develop until in July, or later. The adults from the overwin- 

 tered larvae begin to emerge toward the last of May, and continue 

 emergence through June or until the latter part of July, or later. 

 Probably all are out by the first to middle of August. 



FIRST GENERATION. 



The overwintered broods of adults begin to deposit eggs about the 

 first of June and continue doing so until August, or later, but the 

 principal period of attack is during June and July. The larvae begin 

 to hatch early in June, and begin to transform to pupae and adults 

 early in July, the principal transformations being in July. The 

 broods of adults begin to emerge about the middle of July, the prin- 

 cipal period of emergence being in the latter part of July, but they 



