They mine the pith of the terminal growth, causing more damage as they grow. Large larvae move on to new tissue, cones or shoots. Pupation occurs inside the terminals and cones. Adults lay eggs from late June through August. There is one generation per year.
Adults are a rusty brown.
The larvae are reddish-yellow caterpillars with a black head and dark area behind the head. They overwinter as partially grown larvae within pitch nodules. Feeding resumes in spring and pupation follows in late spring. Adult flights typically peak in late July and early August. Eggs are laid on needle sheaths and the newly hatched larvae feed on young needles, later tunneling into shoots.