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MPB Life Cycle
The MPB generally has a one year life cycle, although during warmer summers
adult beetles may reemerge and lay a second group of eggs in the same year.
At higher elevations, it may take two years for insects to mature because
of cooler temperatures. In mid-summer the female adult bores through the
bark and constructs an egg gallery in the inner bark. She lays eggs in
this gallery that hatch about a week later and become larvae. The
larvae bore new galleries in the inner bark (phloem) and spend the winter
in this stage. The next spring the larvae continue feeding and mature
into pupae. The pupae are still under the bark and within weeks become
adult beetles. The adults initially feed under the bark and then emerge
in mid-July to August depending on the year. These adults begin a new
cycle as they attack green trees.
Attacking Adult |
In Montana, adults emerge in middle to late July and early August. The actual time of emergence varies each year depending on temperature. Most adults emerge during a rather limited time period of 1 week to 10 days. Once they have emerged, they attack green trees and build egg galleries. |
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www.bugwood.org |
| Adult mountain pine beetles are about 1/4" long with black bodies |
Eggs |
| Eggs are laid in alternate groups along the sides of the galleries. Eggs hatch within about a week of being laid. |
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www.bugwood.org |
| Small white oval eggs are laid along the gallery at the end of the needle |
Larva |
| Larvae feed in the phloem and make tunnels at tight angles to the egg gallery. They go through several growth stages before cold weather arrives when they become dormant. The larvae spend the winter under the bark of infested trees. These trees retain their green crown through the winter. In April, they resume feeding and complete their development in June. Infested trees will usually begn to fade and foliage turns yellow as the weather warms. |
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www.bugwood.org |
| They vary in size with time since they hatched from the egg. |
Pupa |
The larva pupates in cells in the bark in June
and turn into adults. These new adults feed briefly in the bark before
emerging in mid July to early August. The foliage of infested trees
turns red as the adults are emerging. |
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www.bugwood.org |
| The pupa has the characteristic form of an adult but is white to light brown in color. |
