154 AGRICULTURAL EXPERIMENT STATION. 



Chrysalis — Lighter colored than the larva and with transverse 

 rows of minute spines on the back. - (Fig. 1, b.) 



LIFE HISTORY. 



The perfect insect makes its appearance in June and Jul}', and 

 remaining concealed during the daj' is not commonly seen. It 

 becomes active at dusk and lays its eggs, one by one, on the bark, 

 near the base of the tree. The eggs hatch in about two weeks, and 

 the young worms begin at once to grow into the tree. The larva is 

 three j'ears changing to the beetle and injures the trees that length 

 of time. The first year the larva works in the sapwood and inner 

 bark, producing flat cavities filled with sawdust like coatings. The 

 second summer the larva is about half grown and does great damage 

 to the sapwood. At the close of the third season, it bores deeper 

 into the wood making a cylindrical channel upward and then outward 

 to the bark, filling the upper part with a powdery material. It 

 retreats to the deepest part of the channel, fills up the passage below, 

 turns around and waits until the following spring when it sheds its 

 skin and becomes the chrj^salis. (Fig. 1. b.) In two or three 

 weeks the chrysalis changes to the beetle form, which opens the 

 upper part of the channel, gnaws a hole through the bark, escapes, 

 and in due time laj'S eggs, completing the life history. 



REMEDIES. 



The dark colored spots made in the bark where the 3'oung worms 

 enter should be scraped until the light colored bark below is exposed 

 and the larva found and destro^'ed. The best time to examine is 

 early in September or a little later in our climate. Sometimes the 

 bark of the dark colored spots cracks and the sawdust like coatings 

 fall out or protrude showing the location of the worm. The earlier 

 the worm is detected the better, as it is more easily removed when 

 young, and less injury is done to the tree. The burrow becomes 

 larger and deeper as the worm grows and can then be best reached 

 by thrusting a stout wire into the hole, or opening it above and 

 pouring in scalding water slowl\% until it reaches the insect and kills 

 it. The practice of digging out the larva from a deep channel is 

 not to be recommended, as it does much injury to the tree. A 

 preventive remedy is the best if an effective one can be found. 

 Various substances have been applied to the trunk of the tree to 



