PEACH INSECTS 



279 



broods greatly overlap, making it very difficult to determine 

 accurately the number of generations a year. The evidence 



Fig. 240. — Burrows of the fruit-tree bark-beetle ; (e) entrance hole, (e.t.) 

 egg tunnel cut by adult, (Ig) larval gallery, (p.c.) plugged entrance to pupal 

 cell. Redrawn after Swaine. 



available goes to show that in the North there are probably 

 two generations, while in the South there are three, four or 

 even more. The winter is passed as larvae either partially 

 grown in the burrows or full-grown in the pupal chamber. 



These bark beetles do not _ 



seem to be able to breed 

 either in healthy, strongly 

 growing trees or in entirely 

 dead dry branches. They 

 prefer trees that have been 

 weakened from injury, lack 

 of care, or from some other 

 cause. Still when very 





Ik;. 2 11. — Section through bark and 

 wood of apple branch infested with th(! 



abundant they will attempt fruit-tree bark-bectlc showing its burrow 

 ■^ ' filled with frass and the larva in its 



to enter perfectly healthy pupal cell. Enlarged. 



trees, selecting those parts 



where the vitality is lowest. In the case of stone fruits 



they are either driven out or killed ])y the copious flow of 



