21. Most feed on fungi, others are carnivores and eat small arthropods such as bark beetles . 22. Colorado s forests are densely wooded, making them much more susceptible to bark beetle attack. 23. There are several types of pine bark beetles , and all have a similar life history. 24. Bark beetles fly in, bore through the tree's bark, and lay eggs under the bark.25. E-Myrcenol acts also as a pheromone for bark beetles . 26. Multistriatin is a pheromone produced by female elm bark beetles , which can be produced synthetically. 27. Two species of bark beetle , no larger than a pencil's eraser, are ravaging drought-weakened forests. 28. SCI-BARK-BEETLES ( Plains, Mont . )-- Bark beetles are becoming a growing problem around the West. 29. The disease dissolved the bark and entered the wood, leaving the tree vulnerable to bark beetles . 30. Several trees also fell after being weakened by fire and a previous infestation of bark beetles .