Bark beetles have diverse and varied life cycles depending on the species and location of the pest populations. Adults bore through the bark and make an initial gallery between the bark and the wood where the eggs are laid.

small white-transluscent oblong larvae in sawdust

Bark beetle eggs in a gallery. Eggs are creamy white and very small. Exact size depends on the species. Photo by William M. Ciesla, Forest Health Management International, Bugwood.org

Eggs hatch and the larvae mine galleries that branch out from the initial egg gallery. The larval feeding is the primary cause of damage from pest species. Different genera and species of bark beetles may produce distinct galleries.

When larvae are mature they pupate and emerge as adults. The majority of bark beetles’ lives are spent beneath the bark. Only adults emerge from the tree and usually it is in the spring to find a new host. Some species emerge as adults in the fall and drop to the soil where they spend the winter insulted from the cold and emerge in the spring to find new host trees.

Bark beetles will attack conifer or hardwood trees depending on the insect species. The native bark beetle pests in Alaska and the potential invasive species of concern are all conifer, mostly spruce, pests. All of our native and ornamental spruce trees are potential hosts for invasive bark beetles.