The forest tent caterpillar, Malacosoma disstria (Htibner), is a common defoliater of deciduous trees throughout most of the United States and Canada. It is a well known outbreak species, whose populations erupt periodically (every 10 to 16 years) when forest conditions are suitable. Typical outbreaks last three to six years in a given geographic area and then collapse as quickly as they arise. This note documents the relation between forest tent caterpillar egg hatching in the field and heat accumulation (degree-days) leading up to hatch. This information will permit (a) predicting the date on which eggs will hatch by summing degree days during the insect's overwintering period, and (b) comparing with populations in other years and areas. The data came from an outbreak in northern Minnesota that began near International Falls in 1966 and collapsed in 1972 (Witter et al., 1975).
Mattson, William J. Jr. and Erickson, Glen W.
"Degree-Day Summation and Hatching of the Forest Tent Caterpillar, Malacosoma Disstria (Lepidoptera: Lasiocampidae),"
The Great Lakes Entomologist: Vol. 11
, Article 7.
Available at: http://scholar.valpo.edu/tgle/vol11/iss1/7