The
Mountain Pine Beetle Life Cycle
HOW A TINY BEETLE KILLS HEALTHY PINE TREES IN JUST ONE SEASON
Summer
Adult Flight &
Tree Invasion
Fall
Egg Laying Beneath the Bark
Winter
Larvae
Overwinter
Spring
Pupation
Begins
Early Summer
Adult
Maturation
Summer
Spread & Cycle Repeats
Adults emerge in mid-to-late summer and attack healthy pine trees. Females release pheromones that attract other beetles, allowing them to overwhelm the tree’s natural defenses.
After mating, females carve galleries beneath the bark and lay up to 75 eggs in protected chambers, creating the next generation of mountain pine beetles.
Eggs hatch in 10–14 days. White, legless larvae tunnel beneath the bark and feed through winter, surviving freezing temperatures naturally.
As temperatures rise, larvae transform into pupae inside protected chambers beneath the bark before emerging as new adults.
New adults remain beneath the bark while their exoskeleton hardens. They also carry blue-stain fungus, which helps weaken and kill the host tree.
By summer, adults emerge from infested trees and fly to nearby healthy pines. During outbreaks, thousands of trees can be attacked across a region.
Important Notes
1-Year Life Cycle
Most Colorado mountain pine beetles complete their life cycle in approximately one year.
HIGH-ELEVATION
DEVELOPMENT
In colder mountain forests, development may take up to two years.
EXTREME COLD
Larvae cannot survive temperatures below -40°F (-40°C)
BLUE-STAIN
FUNGUS
Blocks the tree's water transport system and accelerates tree death.