Notes on the Biology of Ips pini in Central Wisconsin Jack Pine Forests

The biology of the pine engraver, Ips pini (Say) (Coleoptera: Scolytidae), was investigated employing caged and exposed jack pine logs in central Wisconsin in 1957-59. The beetle overwintered only as mature adults in soil and litter. Spring flight normally occurred following a period of about 1 week, during which ambient temperatures averaged 16.7°C, with little or no rainfall. A single male was able to mate 1-6 females, and each female laid 4-5 eggs per day, or 146 eggs during its lifetime. Head capsule measurements revealed 3 larval instars. The complete cycle, including mating and oviposition, required 33-35 days. Mature adults may delay emergence an additional 6-11 days. Inter- and intra-specific competition for food and space was severe. Thanasimus dubius (F.) was the most abundant and efficient predator. No parasites were noted. The top surface of logs in light to moderate shade was most heavily infested. The seasonal history of the pine engraver closely approximated Canadian and other northern United States data.