11. $2 million to combat the spruce bark beetle investation on Alaska's Kenai Peninsula 12. Some olfactory signals directly from other bark beetles , but also some compounds from trees. 13. As the tree declines, more bark beetles are attracted and more cankers are formed. 14. Bark beetles were killing more than twice as many trees as a decade earlier.15. The hickory bark beetle probably destroys more sawtimber-size mockernut trees than any other insect. 16. In Colorado, the pine bark beetle is a common parasite. 17. Later, bark beetles ( " Pseudopityophthorus pubipennis " ) produce fine, red boring dust. 18. Bark beetles communicate with one another using semiochemicals, compounds or mixtures that carry messages.19. Previously, cold spells had killed off bark beetles which are now attacking the forests. 20. Only the natural stereoisomer, ?-multistriatin, attracts the elm bark beetles .
