The Black Spruce. 



297 



habits, the Apate rufipennis Kirby, 1 but the former is evi- 

 dently the chief agent in this unprofitable business. These 

 insects excavate their passages between the bark and the 

 wood, eating away a part of both. Their extended work is 

 therefore equivalent to a girdling of the tree. Their numer- 

 ous galleries form an intricate network of furrows on all sides 

 of the trunk, and traverse one of the most vital parts of 

 the tree, the newly formed and forming layers of wood 

 and bark. The furrows are shallow on the surface of the 

 wood, rather more than half their diameter being in the 

 bark, but their effect is to interrupt the circulation of the 

 nutrient juices and finally to destroy all vital action. The 

 perforations in the bark, by admitting moisture, doubtless 

 work more or less injury. The surface of the sap-wood 

 and the corresponding inner surface of the bark of living 

 trees are discolored for a short space on both sides of the 

 furrows, as if the injury exerted a poisonous or deadening 

 influence on the tissues in its immediate vicinity. This 

 was clearly seen in a tree which had been but slightly in- 

 jured, there being but few furrows and these merely longi- 

 tudinal ones without lateral branches. Each occupied the 

 center of a discolored stripe about half an inch broad, but 

 which usually extended from two to four inches up and 

 down beyond the extremities of the furrows. In another 

 tree there were groups of furrows separated by considera- 

 ble intervals, the central portions of which intervals had a 

 whitish, fresh appearance when the bark was first peeled, 

 but after a few moments of exposure to the air the whole 

 surface of the wood had changed to a dull, dead, brown 

 color, indicating a diseased or unnatural condition of the 

 surface tissues. The foliage on this tree had not yet lost 

 the green hue of life but had commenced falling to the 

 ground. 



1 1 am indebted to Messrs. J. A. Lintaer and J. L. Leconte for the ento- 

 mological names of these insects. 

 Trans. viii.~] 38 



