THE PINE INVESTIGATION. 351 



duced that there was no longer any danger of its killing any 

 more timber. 



2d. That the remaining healthy timber was threatened with 

 an invasion of other bark beetles which had heretofore occupied 

 the role of allies to the destructive species. 



3d. That the trouble would probably be continued in the pine 

 primarily by the turpentine bark beetle, Dendroctonus tere- 

 brans, with Tomicus pini, 2omicus caelatus, Tomicus calli- 

 graphus and Tomicus cacographus as its principal and most ef- 

 ficient allies in causing the death of the trees. 



4th. That the trouble would probably be continued in the 

 spruce by the spruce bark beetle Polygraphus ruftpennis with 

 Dryocoetes autographus and Dryocoetes granicollis as its prin- 

 cipal allies, aided by Tomicus caelatus and the spruce timber 

 beetle Xyloterus lineatus. 



CONDITIONS REPORTED TO THE OWNERS OF TIMBER, 



Upon my return to the Station from the investigations men- 

 tioned above, the following letter was addressed to the repre- 

 sentatives of the several timber companies who had contributed 

 to the expense of importing the beneficial insect: 



(Copy of letter to timber companies owning white pine and 

 spruce timber, dated May 27th, 1893.) 



"I have just returned from the spruce forests in Randolph county, 

 where I distributed the last of the first lot of the German insects. During 

 my absence 330 more specimens came from Germany. Your share of 

 these is 66, which I mail to you to-day. 



During my investigations in the white pine and spruce, I found that all 

 of the trees that died last summer bore abundant evidence that their 

 death had been caused by the destructive pine bark beetle. This species 

 has, however, been greatly reduced in numbers, which would indicate that 

 for a time, at least, no more timber will be killed by it. In fact, it is my 

 belief that the German insects we are introducing may prevent them from 

 ever increasing to sufficient numbers to cause further loss of timber. The 

 most we have to fear at present is the possibility and probability of other 

 bark beetles (which have increased to such great numbers in the dying tim- 

 ber) attacking the healthy timber and continuing the trouble. One of the 

 species, which has been able to multiply in this way, is especially threat- 

 ening to the white pine. It is the large turpentine bark beetle (Dendroc- 

 tonus terebrans) which I found attacking living trees. It has lately ap- 

 peared in different sections of the State in immense swarms, and I found 

 them attacking all of the species of pine. Therefore, with this new fea- 

 ture of the trouble appearing this spring for the first time, it is impossible 

 for us to judge to what extent the timber will be killed before the German 



