142 



IlfjURIOUS INSECTS 



also frequently penetrates into the solid heart wood, while 

 the one under consideration is often found in a full 

 grown state just under the inner bark, or in the sap 

 wood. The usual course of its life however runs as fol- 

 lows: 



As winter approaches, the young borer descends as near 

 the ground as its burrow will allow, and doubtless remains 

 inactive until the following spring. On approach of tlie 

 second winter it is about one-half grown, and still living 

 on the sap-wood; and it is at this time that these borers 

 do the most damage, for where there are four or six in a 

 single tree, they almost completely girdle it. During 

 the next summer, when the worm has become about 

 three-fourths grown, it generally commences to cut a 

 cylindrical passage upward into the solid wood, and be- 

 fore it has finished its larval growth, it invariably extends 

 this passage right to the bark, sometimes cutting entirely 

 through a tree to the opposite side from which it com- 

 menced; sometimes turning back at different angles. It 

 then stuffs the upper end of the passage with sawdust- 

 like powder, and the lower part with curly fibres of wood, 

 after which it rests from its labors. It thus finishes its 

 gnawing work during the commencement of the third 

 winter, but remains motionless in the larval state until 

 the following spring, when it casts off its skin once more 

 and becomes a pupa. After resting three weeks in the 

 pupa state, it appears as a beetle, with all its members 

 and parts at first soft and weak. These gradually harden, 

 and in a fortnight more it cuts its way through its saw- 

 dust-like castings, and issues from the tree through a per- 

 fectly round hole. Thus it is in the tree a few days less 

 than three years, and not merely two years as Dr. Fitch 

 suggests. 



Remedies. — From this brief sketch of the Eound- 

 headed borer, it becomes apparent that plugging the 

 holes to keep him in, is on a par with locking the stable 



