An adult female mountain pine beetle deposits her eggs in egg galleries within the phloem of a Pinus tree, and the eggs lay dormant for 10-14 days before hatching. Larvae then hatch from the eggs, appearing white with brown heads and no legs. These larvae develop through their instars for approximately ten months. Development time varies, depending on the temperature of the phloem in which the larvae are found; colder phloem results in prolonged development, while warmer phloem can shorten the duration of development. By the time winter arrives, the larvae have reached their third or fourth instar, which are much more durable in cold weather. The instars metabolize glycerol during this time, which prevents them from freezing. At the end of their development, around June of the following year, Dendroctonus ponderosae larvae build oval cells stemming out from their egg gallery. Within the oval cell each individual larva develops into a pupa. This stage is normally complete by the end of June or July. After a month or so this pupa develops into an adult. The adults can feed on bark within reach of their oval cells until they break into other oval cells or penetrate the bark to emerge from the tree. For the beetles infesting Pinus trees, this normally takes place in mid-August. At that point the adult females fly to new Pinus trees, secrete pheromones to attract males, and begin penetrating the tree bark to form new egg galleries. When males arrive, they also secrete pheromones to attract more beetles to the location, then fertilize the females beneath the bark of the Pinus tree. From here, the cycle starts again.
Development - Life Cycle: metamorphosis