FEEDING RESPONSES OF THE GUM LEAF SKELETONISER URABA LUGENS WALKER TO SUGARS, AMINO ACIDS, LIPIDS, STEROLS, SALTS, VITAMINS AND CERTAIN EXTRACTS OF EUCALYPT LEAVES

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Abstract
Components of the leaves of species of Eucalyptus were bioassayed using Uraba lugens. Lyophilised leaf powder added to plain diet (cellulose and agar) indicated that feeding rates upon different eucalypts were similar until the proportion of leaf powder in diets reached 4.5% when diets gave the same distinctive results as fresh leaves. The factor(s) responsible for food plant selection by caterpillars was retained in prepared leaf powder and was available for extraction and further testing. Using the plain diet and a diet containing 0.1 M sucrose (standard diet) tests determined the biting and feeding responses of larvae. The major phagostimulants were sucrose, fructose and ascorbic acid. Most substances tested had little or no effect upon larval feeding and were classified as inert (not different from plain diet). Others appeared to enhance larval behaviour only when combined with other substances such as sucrose; these were recorded as synergists. Feeding deterrents or antifeedants were also found. Irrespective of the effect that substances had upon larval behaviour, we recognised that they may have been essential dietary components.