420 



WEST VIRGINIA EXPERIMENT STATION 



the sap and prevent the formation of the new wood * * and 

 the tree languishes and prematurely decays." My observation 

 lead me to conclude that even when our common form occurs 

 in great numbers it is not capable of killing trees. After the 

 great swarms of this species in May, 1893, it attacked the base 

 of the trunk and roots of healthy pines of all kinds and some 

 vigorous Norway spruce trees in Morgantown, and while it 

 was capable of excavating galleries and even developing broods 



in the bark, none of the invaded 

 trees appeared to suffer in the least 

 from their presence, and the wounds 

 subsequently healed. 



As a confederate of Dendroc- 

 tonus frontalis and other insects 

 which cause injuries that weaken 

 the vitality of the trees, the tur- 

 pentine beetle may assist greatly in 

 killing them, or may alone prevent 

 their recovery. In this manner 

 this species may be classed as a sec- 

 ondary destructive enemy of coni- 

 fers. 



KIND OF TREES ATTACKED. 



I have found it attacking all of 



Fig.'LXXIX- Gallery of D. tere- nn| . na fi v p en^pipe nf rn'na fho no 

 brant in living tree, healing over. OU1 native Species OI pine, tne na- 

 tive spruce, the cultivated spruce 

 and a cultivated pine. 



Occurrence. It was exceedingly common during the inva- 

 sion by Dendroctonus frontalis, and occurred in enormous num- 

 bers during the spring of 1893. After that it gradually became 

 less common and since 1895-96 has been rare. 



NATURAL ENEMIES. 



Insects. This bark beetle appears to have but few insect 

 enemies. The following are all that I have noted: 



Thanasimus dubius- Adults observed April 30, 1893, at- 

 tacking and killing adults of Dendroctonus terebrans* an4 OB 



