Location of minimum recording thermometers on ponderosa pine trees in the 1938-1939 temperature study.
Photo by: F.P. Keen and J. Whiteside Date: April 1939
Credit: USDA Forest Service, Pacific Northwest Region, State and Private Forestry, Forest Health Protection. Collection: Bureau of Entomology, Portland Station Collection; La Grande, Oregon. Image: PS-442
To learn more about this photo collection see: Wickman, B.E., Torgersen, T.R. and Furniss, M.M. 2002. Photographic images and history of forest insect investigations on the Pacific Slope, 1903-1953. Part 2. Oregon and Washington. American Entomologist, 48(3), p. 178-185.