INSECTS AFFECTIN(; FOREST TREES. 483 



The galleries of this insect are very characteristic, and frequently afford one of 

 the readiest means of recognizing the species. The exterior signs of its presence 

 may be limited to numerous circular holes about 'g of an inch in diameter or 

 very few of these may be found. This frequently occurs in cases where beetles 

 have entered the bark in large numbers but have not emerged. The entrance is 

 usually effected under a projecting scale of bark and is therefore not conspicuous, 

 \\hile man}' of the exit holes (plate 6, figure i) occur on the prominent ridges and 

 are therefore very easily detected. This species under certain conditions, attacks 

 living tissues and in that event its presence is indicated by brownish or whitish 

 pitch tubes which may be nearly /i an inch in diameter and almost that in height. 

 One of these structures is represented in profile at plate 3, figure 4, and a close exami- 

 nation would show that it was built up with particles of pitch brought out from the 

 burrows by the beetles. Plate 3, figure 2, shows a portion of a pine trunk with a 

 number of pitch tubes, indicating that the tree was alive when attacked. The pitch 

 tubes are located, as a rule, over the central chamber, from which the females make 

 their galleries, usually following the grain of the bark. Plate 3, figure 3, represents 

 the inner side of a piece of bark and shows one of the central chambers with five 

 galleries extending therefrom. The small larval burrows may also be detected in the 

 lower portion, and it will be seen that they are placed at somewhat regular intervals, 

 originating in small notches gnawed at these points by the female. Occasionally eggs 

 are deposited very largely on one side of the gallerv, and in many instances on both 

 sides. The lar\-al mines dilate gradually with the growth of the young and usually 

 have a somewhat serpentine course, terminating in the oval pupal cell. In badly 

 infested trees, they may form masses of interlacing galleries, and it frequently hap- 

 pens that the beetles are so abundant as to eat away and destroy most of the inner 

 bark, as represented at plate 5, figures i, 2, 3. The pitiful condition of a badly 

 infested tree, a few years after being attacked, is shown at plate 4, figure i. It will 

 be seen that most of the bark has dropped from the trunk and plate 3, figure I, shows 

 the many shallow grooves in the exposed wood. The work of this insect is so incon- 

 spicuous that at times few exterior indications ma)- be seen. Plate 6, figure 2, shows 

 the base of a tree, the inner bark of which has been riddled by this borer, as repre- 

 sented at figure 3 of the same plate. It will be observed that the interior is nothing 

 but a decaying mass of borings, and the few e.xit holes occurring in such a piece of 

 bark are represented at plate 6, figure i. The galleries of this species arc sometimes 

 preserved for an indefinite time by the infiltration of pitch, plate 5, figures 2 and 4, 

 and this is incontrovertible ex'idence of li\-ing tissues having been attacked. 



Tlie work of this species on two trees in association with others is shown at plate 



