n 



and together they excavate a broad primary or egg gallery (PL III) 

 up through the inner bark, often grooving the surface of the wood, 

 for a distance of from 2 to 9 inches. Along the sides of this gallery, 

 which is usually about three times as broad as the beetle, the eggs 

 are placed singly in small cavities or in groups along a notched 

 groove. The eggs are then protected by a mass of borings cemented 

 with gum, which are closely packed, filling up the broad egg gallery, 

 with the exception of a small central burrow which is left or is subse- 

 quently excavated through the middle of its entire length. The 

 original entrance is first packed, then an opening to the outside is 

 made in the roof of the gallery a few inches from the entrance, 

 another section is excavated and packed and another hole is made 

 through the roof, and so on until the gallery is completed. After all 

 is finished the adults make one or two irregular lateral branches at 

 the farther end, apparently for an abiding place until they die. 



The gum flowing into the wound made by the beetle when it is 

 excavating the entrance is pushed out and a hole kept open through 

 it, thus forming what is known as pitch tubes, which are so conspicu- 

 ous on the bark of recently attacked trees. After the vitality of a 

 tree is weakened by numerous wounds and an excessive flow of resin, 

 the entrances subsequently made are not marked by pitch tubes; or 

 if a tree is decidedly weakened from other causes before it is attacked, 

 pitch tubes will not be formed. 



When numerous beetles are boring into the outer bark the dry dust 

 falls down and lodges in the flakes of bark and the moss on the tree, 

 so that a freshly attacked tree may be identified from its presence. 



The secondary or larval mines. — When the eggs hatch, the minute 

 white grubs or larva3 eat their way into the soft inner bark, which by 

 this time has commenced to die and is in the best condition for their 

 food supply. When the eggs are placed in separate cavities each 

 larva makes a separate mine, but when they are massed along the 

 sides, or placed close together, they work side by side and consume 

 all of the inner layer of bark until they have progressed some dis- 

 tance, when they begin to separate and each larva makes an inde- 

 pendent mine. (PI. IV.) While the individual burrow may cross 

 and recross those of its neighbors, it preserves a course of its own 

 and increases in width as its occupant increases in size until the larva 

 attains its full size and ceases to feed. It then excavates a cavity 

 either in the bark next to the wood or next to the outer dry bark, 

 where in due time it changes to the pupa. Here it remains in a semi- 

 dormant condition until the legs, wing covers, and other parts develop. 

 It then sheds its outer skin and becomes an adult winged beetle, soft 

 and yellow at first but gradually hardening and becoming darker. In 

 due time the mature beetle bores its way out to the surface and 

 emerges to fly about in search of a tree in which to excavate galleries 

 for another brood. 



