27 



Maine. It belongs to the same family of beetles as the true destroyer, 

 but to an entirely different genus. The specific name, rufipennis, 

 given to it by Kirby, is unfortunately the same as that he gave to the 

 Dendroctonus described from the same region. This has caused 

 much confusion in the writings of entomologists and others relating 

 to the insect enemies of the spruce. 



This species is enormousty abundant in all injured and dying stand- 

 ing trees, and in the bark of the branches, tops, and stumps, in 

 cuttings, windfalls, etc. (PL VIII, e, and PI. IX.) Its abundance, 

 together with its habit of infesting the tops of trees immediately after 

 the middle portion of the trunk or base has been attacked by the 

 spruce-destroying beetles, renders it one of the most efficient allies 

 of the primary enemy. 



The adult is a small black beetle about .08 of an inch long and .01 

 of an inch broad. It is easily distinguished from all other spruce 

 bark beetles of similar size and form by the fact that each of its com- 

 pound e}^es is divided b} 7 a smooth narrow space. It passes the win- 

 ter in all stages within the bark of spruce stumps, logs, and the tops 

 of felled and standing trees. 1 



THE SPRUCE TETROPIUM. 



This is the round-headed bark and wood-miner which was found to 

 be so common in the spruce of West Virginia in 1891, where its work 

 contributed to the rapid decay of the wood of dead trees. 2 It is very 

 common in the spruce of Maine, where it was observed by the author 

 in the stumps and logs of recently felled trees and toward the base 

 of trees attacked by the spruce destroyer. Indeed, an attack by the 

 latter is followed almost immediately by the Tetropium adult, which 

 deposits its eggs in the outer bark from toward the middle of the 

 trunk to the base. The young larvae are capable of mining through 

 the living bark (PI. X) and continuing their work regardless of the 

 sap and pitch. Therefore, this insect must be classed as one of the 

 principal aids to the spruce beetle in not only causing the death of 

 the trees, but in contributing to the rapid decay of the wood. 



OTHER INSECTS. 



Numerous other insects which aid in causing the death and decay 

 of spruce might be mentioned (Pis. VIII, XI, and XII), but the two 

 just referred to are by far the most important. There maj 7 , how- 

 ever, be an exception in the defoliating insects (PI. XIII), which, it 

 is believed, may contribute greatly to produce favorable conditions 

 for the attack of the spruce-destroying beetle. 



1 For a more detailed account of this beetle see Bulletin 56, W. Va. Agricultural 

 Experiment Station. "Report on Investigations to Determine the Cause of 

 Unhealthy Conditions of the Spruce and Pine, from 1880 to 1898," pp. 246-251. 



2 Ibid., pp. 239-242, 259, 438. 



