Mountain pine beetles/larvae tunneling in bark

Here, scientists point to a mountain pine beetle (top) and a pine beetle larva (bottom) that have been tunneling in the bark of a killed pine tree. The bluish streaks in the bark are from bluestain fungus.

Mountain pine beetle outbreaks can result in the loss of millions of pine trees throughout western North America. The beetles lay eggs and develop in the bark of mountain trees, especially lodgepole, ponderosa, Scotch, and limber pines. The beetles carry bluestain fungus spores, which infect the trees and turn the sapwood a bluish color. Both the beetles and the fungi eventually kill their host trees.