THE PINE INVESTIGATION. 



May 31st and October 31st, making a total of 48 generations 

 from the seven different stages between June 20th and October 

 18th. 



HABITS. 



The hibernating adults emerge from the infested trees about 

 the middle of April, and those which emerge between that 

 time and the middle of July, evidently do not attack the 

 healthy, living trees, but excavate their brood galleries in the 

 living bark of trees injured but not killed by the attack of late 

 broods during; the previous fall. By the last of July, as indi- 

 cated by the diagram, a brood of adults has developed from 

 five hibernating stages, and since each adult probably lives a 

 month or more, they occur at this time in great numbers; and 

 as the flow of liquid sap is becoming less profuse under the 

 bark at this season, they begin to attack the living trees. The 

 first, or preliminary attack, HS I have observed, usually fails in 

 killing the tree if it is not followed up by successive and subse- 

 quent attacks. By the middle of August, however, all seven 

 of the separate hibernating broods have developed into adults ; 

 and since by this time the conditions beneath the bark of living 

 trees are most favorable for their operations, they invade the 

 previously attacked, as well as the healthy trees, in enormous 

 numbers, entering the bark first near the top, and later further 

 down the trunk.. The process of excavating the galleries as in- 

 dicated by their form and peculiar characters is as follows : 



The adults (probably both sexes) select a crevice in the outer 

 bark of a living tree, and commence the excavation of the main 

 entrance. The outer or dry bark, is soon penetrated and the 

 more difficult operations of boring through the inner or living 

 bark is continued as the conditions will permit, until the outer 

 layer of wood is reached. If, as is usually the case in a pre- 

 liminary attack on healthy pine trees, there is a profuse flow 

 of sap or turpentine, the burrow is extended laterally through 

 the outer and middle layers of the living bark for some dis- 

 tance (one or two inches) before the inner layer is pene- 

 trated. If there is only a moderate flow of turpentine, the 



