Life History of the Parsnip Webworm, Depressaria pastinacella (Lepidoptera: Oecophoridae), in Central Iowa

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Abstract
Quantitative information on the life history of the parsnip webworm, Depressaria pastinacella (Duponchel), was gathered from three insect populations and their host plants in the Ames, Iowa, area. The eggs are ca. 0.56 mm long and 0.29 mm wide. Both laboratory-reared and field-collected larvae progress through six stadia identifiable by head-capsule-width measurements. Developmental time in the laboratory (egg to adult) is ca. 38 days, including 4 days in the egg stage, 21 days in the larval stage, and 13 days in the pupal stage. A complete and viable second generation seems unlikely in Iowa. Numbers of both eggs and larvae in the field declined dramatically from the first to the second generation, and no second-generation pupae were found. Most eggs are laid on parsnip leaves; most larvae occur in immature parsnip umbels; most pupae are formed within parsnip stalks. Parasitoids, primarily Apanteles depressariae Muesebeck (Hymenoptera: Braconidae), were rare and only emerged from fourth-instar hosts. Overwintering seems to occur in the adult stage, but moths were very difficult to collect in the field.

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