Feeding stimulants of Solanaceae-feeding lady beetle, Epilachna vigintioctomaculata (Coleoptera: Coccinellidae) from potato leaves

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A phytophagous lady beetle, Epilachna vigintioctomaculata, feeds mainly on potato (Solanum tuberosum) leaves. The methanol extracts of potato leaves showed feeding stimulative effects on the adult of the beetle. The feeding stimulants were isolated and identified as methyl linolenate from a lipid-soluble fraction, and glucose and fructose from an aqueous fraction. Although methyl linolenate alone was inactive, it acted synergistically with sugars. Methyl linolenate maximized the feeding activity of sugars at the concentration contained in the potato leaves. It is suggested that methyl linolenate plays an important role in the host selection of E. vigintioctomaculata.