Nine sample plots were established in 1967 in northern Minnesota in areas that had epizoötic population levels of the forest tent caterpillar, Malacosoma disstria Hübner (Lepidoptera: Lasiocampidae). The plots were at least 1 mile apart and each consisted of 5 acres or more of 90–100% trembling aspen, Populus tremidoides Michx. Sampling techniques using the tree as the major unit are described. The 1st life tables and survivorship histograms for the forest tent caterpillar are presented. The survival rate during the egg and pupal stages differed considerably in 1968 and 1969. The differences in egg survival are attributed to fluctuations in rates of death of fully developed 1st-stage larvae within eggs; they ranged from 39% in 1968 to 3% in 1969. Egg parasitization and infertility were 7–10 and 1–3%, respectively, showing no important changes from year to year. The differences in pupal survival resulted from fluctuations in rates of pupal parasitization, mostly by Sarcophaga aldrichi Parker; from 74% in 1968 to 50% in 1969. Generation mortality was 99.3 and 97.8% in 1968 and 1969, respectively. Generation survival equations by plots for 1968 and 1969 are presented.
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Witter et al. (1972) studied this question.