• Shepherd, R.F.
  Forest Zoology Laboratory, Calgary, Alberta
  

In the most severe outbreak areas in the eastern and western parts of North America, the spruce budworm, Choristoneura fumiferrana (Clem.) (Tortricidae), maintains a one-year life cycle. Within the Canadian Rocky Mountains, however, the budworm's life cycle lasts two years, The outbreaks are also quite different in character. The two-year cycle budworm is present in most of the spruce fir stands of this regular, but high populations recur only in certain restricted stands within this spruce-fir forest