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Adults are reddish-brown to black and about the size of a grain of rice. They overwinter in the duff beneath trees and emerge as adults in April and May. Ips bark beetles breed from April until late summer, producing two to three generations each year. Adults can be found making Y- or X-shaped egg-laying tunnels, called galleries, in the inner bark. Small mounds of reddish sawdust on the trunks of pines are evidence of bark beetle attack.
Pine bark beetle to scale.
Larvae are small, cream-colored grubs. They feed on the inner bark and cambium in small tunnels radiating away from egg-laying galleries. Larval galleries are empty during late fall, winter, and early spring.
Exit holes on trees are small, round holes in the outer bark created by adults exiting the tree. A first generation of adults can emerge in late May or June and a second one in July or August. It is possible that a third generation could develop during a particularly hot summer and early fall. A tree that has died from bark beetle attack and has an abundance of beetle exit holes looks as if someone shot it with a shotgun.