i82 Journal of Agricultural Research voi. m, no. 3 



directly through the bark to the cambium, thence through the cambium 

 down the trunk to the ground, whence it proceeds outward through a 

 convenient root. After boring in this manner through the cambium for 

 a distance of from 6 to 12 inches it burrows abruptly into the solid wood, 

 where all the feeding throughout the remaining part of the larval stage is 

 done. For most of its length the burrow through the cambium fol- 

 lows in a general way the grain of the wood. It sometimes zigzags 

 across the grain directly after leaving the egg and invariably winds 

 around the root in a spiral course once or twice just before leaving the 

 cambium to enter the solid wood of the root. The burrow in the cam- 

 bium soon heals and is scarcely discernible a year after it is made. 



After burrowing into the solid wood of the root, the larva continues to 

 feed outward from the tree. If the root is long enough, the burrow may 

 continue toward the tip for a distance of 3 or 4 feet, after which it turns 

 and is directed back toward the base. The larva spends its first winter 

 well out from the trunk, often in a root not more than one-sixteenth of 

 an inch in diameter. In penetrating these smaller roots it converts all 

 the hard wood into powder during its outward and return journey. It 

 is active late in the fall and early in the spring, and probably consid- 

 erable feeding is done during the winter. With the coming of warm 

 weather it feeds rapidly back toward the base of the root, and by mid- 

 summer it has reached the center of the root system and has begun to 

 ascend the body of the tree. The latter part of the summer and the fall 

 are spent in boring upward through the trunk (PI. XXIX, fig. 2) and in 

 fashioning a pupal chamber. In trees that are cjuite small pupation 

 takes place within 5 to 10 inches of the ground, but in larger trees the 

 lar\^ffi for some reason ascend higher before fonxiing the pupal cell. In 

 apple and pear trees that are as large as 6 inches in diameter at the base 

 of the trunk it is not unusual for the larvae to ascend 2 or 3 feet to 

 pupate, and in one case an individual was found in a 12-year-old pear 

 tree that had burrowed up from the roots and pupated in a branch 46 

 inches above the ground. 



The ascent through the trunk is usually made within half an inch of 

 the inner bark, the larva occasionally approaching the bark but never 

 entering it. The pupal chamber is a curved and enlarged terminus of 

 the burrow, occupying a vertical position, with the convex side toward 

 the heart of the tree. The upper end of the chamber curves abruptly 

 to the bark, while at the lower end the curvature is more gradual and 

 the chamber lacks one-sixteenth of an inch or more of extending to the 

 bark. The two extremities are from i inch to iK inches apart, and when 

 the chamber is completed both ends are packed with wood fragments, 

 the insect occupying a space between. 



In forming its pupal quarters the lar\-a first extends a burrow of the 

 usual transverse dimensions through to the bark at the upper end. It 

 then recedes for about one-fourth of an inch and begins eating the wood 

 from the side of the burrow. As this proceeds, the larva directs its 

 excavation backward along the ventral side of its body and so doubles 

 the diameter of the original gallery. The larva thus has its two ends 

 folded closely together, and as the body moves forward the head and 

 anus are soon contiguous. At this point the excavation ceases, and the 

 head turns and follows the anus forward until both extremities are 

 at the upper end of the chamber. Here the head rests, but the hinder 



