Uraba lugens Walker (Lepidoptera: Noctuidae): larval survival and parasitoid biology in the field in South Australia

Twenty-two species were found in the parasitoid complex attacking Uraba lugens Walker: 11 primary parasitoids, 10 hyperparasitoids and 1 facultative hyperparasitoid. All immature stages of U. lugens were parasitised, with larval parasitoids killing hosts from the third instar onwards. The majority of parasitoids were found in both the summer and the winter generations of U. lugens, and at least 4 of the primary parasitoids produced more than 1 generation per generation of the host. Parasitoids were collected from hosts on several species of Eucalyptus. The longevity of adult female parasitoids in the complex varied between 8 and 254 days. Of the hyperparasitoids, many were gregarious and polyphagous, and all but 1 species parasitised the pupae of primary parasitoids.

High mortality occurred among early instar larvae of U. lugens, but older instars were much less affected by mortality factors. The survival of larvae between trees and even between different groups on the 1 tree was variable. Caging of larvae greatly increased overall survival and decreased the fluctuations in mortality between larvae on different trees. Although parasitism was very high in some individual groups, it accounted for only a small proportion of mortality of U. lugens. Hyperparasitism and the presence of many polyphagous primary parasitoids in the complex may be a contributing factor to the low levels of parasitism observed on U. lugens.