THE GENUS DENDROCTONUS. 



91 



SEASONAL HISTORY. 



OVERWINTERING STAGES. 



The winter is passed in the inner bark on trees attacked the 

 preceding summer and fall, as parent adults in the egg galleries, all 

 stages of larvae in the larval mines and transformation cells, and as 

 broods of young adults in transformation cells; but principally 

 as larvae. 



ACTIVITY OF OVERWINTERED BROODS. 



As soon as warm weather begins in April and May the over- 

 wintered parent adults extend their incompleted egg galleries and 



Fig. 51. 



-The Black Hills beetle (Dendroctonus ponderosae): a, Adult; b, larva; c, pupa, a, Greatly 

 enlarged; b, c, less enlarged. (Author's illustrations.) 



excavate new ones in the remaining living bark on the dying trees 

 and deposit eggs. The overwintered broods of young adults begin 

 to emerge from the trees by the middle of July, but the main swarm 

 does not appear until the last of July and first of August. Some of 

 the retarded broods continue to come out until October, or later. 

 The broods of larvae begin to transform to pupae and adults about 

 the middle of May, and continue to do so during the period from 

 June until September, or later, and begin to emerge in August. 



