812 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 



or the attacks of some fungus, would better account for a destruction so 

 widespread and apparently sudden. 



During the last half of the summer of 1881 and subsequent summers, 

 spent in Maine, I was enabled to make n more careful examination into 

 the causes of the disease, and think that without much doubt it was 

 wholly due to the attacks of the caterpillar above mentioned. 



About the middle of July I went from Brunswick, Me., to the White 

 Mountains, and observed a good many dead spruces and firs in the woods 

 on either side of the road from Gorham to the Halfway House upon 

 Mount Washington. The dead spruces and firs were in nearly all cases, 

 especially those which had evidently been cut down during the preced- 

 ing winter (1880-'81), riddled by the mines or burrows of the bark-borer 

 {Xyloterus bivittatus). 



The spruces were also infested by the common longicorn borer, 3£ono- 

 hanimus confusor, the larvse being found to have bored the tree in all 

 directions. 



Living hemlock trees, 15 to 20 inches in diameter, were infested by 

 large unknown longicorn borers under the bark, while the bark itself 

 was mined in all directions by Hadrotrymus, whose burrows were very 

 abundant in logs cut down during the past winter near the Glen House, 

 and in barks stripped from the logs ; and the mines also occurred in the 

 bark of living trees. 



About the 1st of August, during a visit to Peak's Island, in Portland 

 Harbor, large numbers, sometimes entire clumps or groups, of dead 

 spruces were found to have been perforated by small bark -borers; not 

 only the trunks but the larger and smaller branches, the beetles being 

 still at work. Some of the spruces were partly killed, the upper branches 

 retaining their leaves. 



At Brunswick, Me., the dead spruce trees were found to be infested with 

 myriads of three common borers {Xyloterus bivittatus, Xyleborus ccelatuSy 

 and Pityophthoriis puberulus), the bark being mined in every direction, 

 the beetles occurring in the larva and pupa, as well as adult or beetle 

 condition. Some of the trees, only partly dead, had the bark of the 

 trunk and branches filled, so to speak, with these mischievous borers, 

 and the results of their united labors were equivalent to barking or 

 girdling the tree not only in one spot, but the entire tree ; the deadly 

 nature of the attacks of such a host of bark-borers raining and feeding 

 upon the inner bark and sap-wood, the most vital part of the tree, was 

 sufficiently obvious. The stumps of firs and spruces, as well as of white 

 pines, which had been cut down the previous November, were swarm- 

 ing with these small Tomici In all stages of development, their numbers 

 being astounding. In two hours I took 1,000 specimens of Xyleborus 

 aelatus from one pine stump. 



But if there had been any doubt as to the nature of the disease whicli 

 carried off the spruces at Brunswick, in the woods southeast of the col- 

 lege grounds, in the course apparently of a single year, several seasons, 



