522 SKVENTH REl'ORT OF THE FOREST, FISH AND GAME COMMISSION. 



represents a small twig less than ^ an inch in diameter and shows the adult galleries 

 of two females passing from a central chamber around the twig in opposite directions 

 and overlapping each other on the farther side by about ^/^ an inch. 



The larvae or grubs pursue a rather tortuous course at approximately right 

 angles to the parental galleries and end their operations in slightly enlarged ellipti- 

 cal cells where the final transformations to beetles occur. 



LARGE BLACK CARPENTER ANT. 



Cainpfl)iotus Itcrculaiicus Linn. 



This large ant was met with a number of times in the Adirondacks where it had 

 begun to excavate galleries in the balsam, and in some instances its work had 

 progressed to such an extent that the tree was unable to stand a severe storm and 

 had been blown down. 



These insects are unable to enter sound trees, but wherever the wood is exposed 

 they are very apt to effect an entrance. The peculiar method in which these 

 insects work in balsam is well shown at plate 15, figure I. It will be seen that the 

 wood has been eaten away along well-defined lines, leaving large laminre which are 

 connected by irregular oval holes and with the lower ends eaten away entirely. 

 This method of work contrasts verj- strongly with the operations of the same species 

 in elm, shown in plate 15, figure 2. The reason for the difference probably lies in the 

 fact that the balsam toward the end of the growing season deposits a layer of harder 

 wood, which makes it easier to work along certain lines, while the interlacing 

 fibers of the elm present no such difference, all of the year's growth being nearly 

 of the same hardness, and therefore in the latter instance, the ants work in any 

 direction which fancy indicates and follow no definite plan. 



Insects Affecting Arbor Vitae. 



This tree is somewhat common in the Adirondacks and as its wood, frequently 

 used in rustic work, is often artistically carved by a little borer, a brief account of 

 the species is given in this connectioii. 



Plihtosinus dcntatus Say. 



A very interesting beetle, about ' ,0 of an inch long, may be met with in the 

 Adirondacks working in the inner bark of dying and dead arbor vitae. This insect 

 is remarkable for its beautiful galleries and can not be considered an injurious spe- 

 cies, since it is rarely abundant. 



