THE BLACK HILLS BEETLE. 



15 



exception to this is when the top portion of the tree or one side of 

 the trunk is killed the first year and a brood develops in the remain- 

 ing living bark the next year. Tliis sometimes occurs, but is never 

 common enough to require special notice. Its occasional occurrence, 

 however, explains why broods of the beetle are sometimes found in 

 trees which appear to have been dead for two or tliree years. 



LIFE HISTORY. 



The insect passes the winter, or inactive period, in all stages — as 

 larvae, pupae, and adults — beneath the bark of trees attacked by 

 the parent beetles during the previous summer 

 and fall. Activity begins in the spring as soon as 

 sufficient warm weather prevails, when the broods 

 continue to develop and mature, but remain in the 

 bark until about the middle of July (Black Hills, 

 latitude 44°, altitude 7,000 feet), probably later 

 northward and at higher altitudes, and earlier 

 southward and at lower altitudes. When the 

 adults (fig. 1) begin to emerge from the bark of the 

 trees in which they had developed from eggs depos- 

 ited the previous year, they usually fly in swarms, 

 and attack the living trees, in which they excavate 

 galleries tlirough the inner layer of bark and groove piQ 

 the surface of the wood. Along the sides of these 

 primary galleries excavated by the beetle, eggs 



are deposited for the next generation, which, as be- 

 fore, hatch into grubs or larvae (fig. 5), wliich mine at 

 right angles to the primary galleries through the inner 

 bark, on which they feed. This feeding and growing 

 stage continues during the first summer, some of the 

 individuals completing their development before fall, 

 so that all stages, including the pupae (fig. 6), may be 

 found during the fall in the trees attacked in July. 

 These with the younger broods remain dormant dur- 

 ing the winter and complete their development the 

 following spring in time to emerge in their regular 

 course during the following summer. 



The period of fhght of the beetles and of their attack 

 on Hving trees, as well as the egg-depositing period, is 

 about seventy-five days, beginning about the middle 

 of July and ending about the first of October. The exact time of 

 the beginning and ending of this period in a given locality depends 

 upon the latitude, altitude, and local conditions. The normal 

 period of development of a brood from the time the living tree is 

 attacked and the eggs deposited until the adults emerge from the 



Larva of the 

 Black Hills beetle. 

 (Author's illustration.) 



Fig. 6— Pupa of the 

 Black Hills beetle. 

 (Author's illus- 

 tration.) 



