384 ^'E\V YORK STATE MUSEUM 



Life history. The life history of this species has been carefully studied 



by Dr Hopkins, and the following is his summary : 



These observations would also indicate that activity ceases in the fall 

 by about the middle of October, when all stages of the insect may occur in 

 the bark of infested trees where they, with the probable exception of the 

 eggs and pupae, remain until the first week in June. Activity then com- 

 mences, the mature larvae change to pupae, and by the middle of June 

 those that pass the winter in the adult stage emerge and commence to exca- 

 vate galleries and deposit eggs. The adults from the hibernating larvae 

 of different stages, develop and continue to emerge possibly until the last 

 of August. Therefore the eggs deposited by the late developing beetles 

 produce larvae which do not complete their development until July or 

 August of the next year. Thus, the period of development may vary from 

 about 70 days to about 12 months, but all broods from eggs to matured and 

 emerging adults remain in the bark about 12 months, of which they are 

 dormant about seven and a half and active four and a half. 



Natural enemies. This species is subject to attack by several natural 

 enemies. The commonest parasite, according to Dr Hopkins, is Br aeon 

 simplex Cress., a well known species which lives at the expense of a 

 number of wood borers. The antlike clerid beetle, T h a n a s i m u s n u b i- 

 lus KL, is said by Dr Hopkins to be a very efficient enemy of this 

 species. He states that the adult emerges from the bark of infested trees 

 somewhat earlier than the spruce destroying beetle and remains hidden 

 thereon till the bark borers commence to emerge, when it pounces on and 

 devours them. It also follows the beetles to other trees and continues to 

 prey on them, and while it does not enter the galleries, it deposits eggs at 

 their entrances, so that the active reddish larvae hatching therefrom can 

 readily enter and feed on the bark beetle larvae. The clerid larvae on 

 attaining full growth retire to the central Dendroctonus galleries, pupate 

 and transform to the adults. 



Woodpeckers are valuable checks on this species. Professor Peck 

 states that many of the dead trees in two groves observed by him, had 

 their bark so chipped by woodpeckers, that the general hue of the trunk 

 was a reddish brown instead of the usual greenish brown. Dr Hopkins 

 states that he is quite confident that in many hundreds of infested trees 

 examined, at least one half of the beetles and their young had been 



