6 BULLETIN 847, U. S. DEPARTMENT OF AGRICULTURE. 



in the autumn and continues to throw out castings until it begins the 

 construction of its pupal quarters. (PL VII, A.) 



Trees of all ages are attacked, but the most severe injury is done to 

 young trees, in which the wound made is greater in proportion to the 

 size of the trunk. (PL IV, D.) Frequently a number of borers will 

 attack a single tree and girdle it completely or so riddle and weaken 

 the heartwood that the tree will break over at the surface of the 

 ground. It is not unusual to find a dozen borers in one tree, and on 

 one occasion the writer found 25 within an 8-year-old apple tree. 

 Felt and Joutel (6) cite an instance where 30 borers were removed 

 from, one tree. 



Trees severely injured by borers present a sickly appearance, the 

 foliage being sparse and of a pale green color. (PL VI, A.) When of 

 bearing age they are inclined to bloom freely and set heavy crops of 

 fruit, the fruit developing poorly and the trees often dying in an 

 effort to bring the crop to maturity. If any part of an orchard is 

 bounded by woods the first and most severe injury usually occurs 

 among trees near to such woods. 



METHODS USED IN SECURING BREEDING MATERIAL AND REAR- 

 ING THE INSECTS. 



In the rearing work connected with this investigation many indi- 

 vidual insects were carried through from eggs to adults in young 

 apple trees planted for the purpose. Larger apple trees were used in 

 which to plant newly hatched borers for rearing purposes. The 

 trunks of some trees were made to support and bring to maturity as 

 many as 25 borers. Each spring a large number of pupae were se- 

 cured by scouring the roadsides, grown-up fields, and neglected 

 orchards of various localities for small, worthless seedling-apple 

 trees in which the insects were maturing. Such trees were cut near 

 the ground and short sections of the base of the trunk containing the 

 pupae sawn off and taken to the insectary, where they were kept in 

 rearing cages. Many pupae were also chiseled out of trees and placed 

 in small glass vials excluded from the light. About 75 per cent of 

 the pupae kept in the vials developed into normal adults. 



CAGES USED FOR REARING AND OBSERVING BORERS. 



In carrying on the work herein described three types of fine- 

 meshed, wire-screen cages were used. The first were small cylinders 

 fitted around the bases of trees in which borers were developing 

 (PL II). These cages were about 15 inches in length, the lower 

 end when in place being sunk in the earth for half an inch and the 

 space at the top between the wire and tree packed with cotton batting. 

 Such cages excluded woodpeckers, imprisoned emerging beetles, and 



