2o6 



AN ECONOMIC ENTOMOLOGY. 



length. It is not economically important, unlike the " broad - 

 necked Prionus," P. laticollis, whose larvce in blackberry are 

 known as "giant root-borers." The beetle is black, robust, 

 broader than usual, with a broad, toothed thorax, and from one 

 to two inches in length. The larvae are immense, nearly three 

 inches for a full-grown female, and they feed in the roots of a 



Fig. 195. 



The " giant root-borer," Prionus /o/ico/iis.— Larxa, pupa, and adult. 



variety of trees and plants, including chestnut, oak, cherry, apple, 

 grape, and blackberry. They require three years to reach 

 maturity, and are sometimes decidedly troublesome. There is no 

 way of reaching the larvae except to dig them out, and in black- 

 berry fields the sudden wilting of part or all of a hill indicates 

 almost infallibly the presence of one or more, which should then 

 be found and destroyed at once. Grape and apple stand the 

 injury better, but when a tree becomes badly infested nothing 

 remains but to take it out and burn it. Even large trees are 



