Feeding around axis of cone. A proportion of seeds can be consumed by a single caterpillar. Eggs are laid on flowers in early spring.
Young larvae begin feeding on scale tissue but as they mature, feed more on seeds.
By the end of July, they pupate in a tough pitch-coated cocoon in the centre of the cone. Pupae may remain in diapause for 1-3 years in the old cones after they have fallen from the trees. B. colfaxiana occurs throughout the range of Douglas-fir but more frequently and causes more serious damage in drier interior regions.