The bionomics of the red pine shoot moth, Dioryctria resinosella Mutuura, a newly described species of shoot borer in red pine, Pinus resinosa Ait., were investigated in Wisconsin sand plains plantations. The appearance of eggs, larvae, pupae, and adults are described. Head-capsule measurements indicated five larval instars. First-instar larvae overwintered in hibernacula. Shoot feeding was generally initiated by third-instar larvae in late May. Cones also were attacked. Pupation occurred in July. The flight period extended from mid-July to mid-September. The sex ratio was 0.53. Only red pine shoots and cones were attacked in a mixed pine stand. Infestation rates were highest along plantation edges, in the top half of the crown and in plantations greater than 20 years of age. Hyssopus rhyacioniae Gahan occurred most frequently among parasitoids reared from larvae and pupae.