The Parasite Complex of the Forest Tent Caterpillar 1 in Northern Minnesota 2

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Abstract
The parasites of the forest tent caterpillar, Malacosoma disstria Hübner, were studied during the last 6 yr of the 1964–72 outbreak in northern Minnesota. Egg parasitism, only ca. 4–10%, involved 3 species: Telenomus clisiocampae Riley, Ooencyrtus clisiocampae (Ashmead), and Tetrastichus silvaticus Gahan. Twenty-five hymenopterous species and 13 dipterous species were reared from the larvae and pupae of the forest tent caterpillar. Six of the hymenopterous species were hyperparasites, while 6 of the dipterous species were scavengers. Rogas sp. was the only early larval parasite. The most abundant late larval parasites were Patelloa pachypyga (Aldrich and Webber), Leschenaultia exul (Townsend), Lespesia frenchii (Williston), and Trichonotus analis (Say). Pupal parasitism was highest on cocoons from the ground level and progressively lower in the shrub and crown levels. Pupal parasitism increased with age of the infestation until 1968, decreased significantly in 1969, then increased again until the population collapsed in 1972. Sarcophaga aldrichi Parker and tachina flies accounted for 98% of all parasitism in the late cocoon collection during 1967–71 except in 1970. S. aldrichi destroyed all other parasites in the pupae and became the over-whelmingly dominant parasite in pupae after the 1st year of heavy infestation. Itoplectis conquisitor (Say) was common during the 1st year of heavy infestation. Otherwise, ichneumon wasps were rare in the late cocoon collections except in areas at the edge of the outbreak. The biology and individual patterns of parasitism during the outbreak are discussed for the common parasites.

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