On successfully attacked trees, the foliage may thin, yellow, or redden. Adult fir engravers average about 4 mm in length. They are black and the posterior of the abdomen is prominently concave on the underside. Larvae are small and white. Adult insects emerge and fly in search of new hosts from June to September, with the greatest emergence in mid-July.
Attacks seem to be made at random on both resistant and susceptible trees.
Females attack trees first, tunnel into the inner bark, and await the males in the nuptial chamber. Other females will attack the same tree after a first attack, particularly if the first attack was successful. After mating, the female will tunnel horizontally from the nuptial chamber, depositing eggs in niches cut in the walls. In contrast to Douglas-fir and mountain pine beetles, fir engravers are not very tolerant of the resins produced by resistant trees, and will readily abandon the attack if they incur too much resistance. Furthermore, eggs laid in resistant trees will be poisoned by these resins.