• Kemp, W. P
  University of Idaho
  
• Everson, D. O.
  University of Idaho
  
• Wellington, W.G.
  University of British Columbia
  

The western spruce budworm (Choristoneura occidentalis Freeman) has been reported in Western North America since the early 1900s, but only relatively recently have reasonably precise geographic locations been recorded (Dolph 1980; Fellin, personal communication; Johnson and Denton 1975). The western spruce budworm reaches outbreak densities in only certain parts of its range, but the reasons for this pattern are still unknown. This study was designed to test the hypothesis that, if climatic characteristics are important to budworm development and survival, then regional outbreak frequency should be related to regional climatic conditions.