The host specificity of phytophagous beetles (by the aid of Cucurbitaceae-feeding beetles

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The host specificity of Cucurbitaceae-feeding beetles is explained by the existence of cucurbitacin in the host plants. The author investigates the feeding stimulants of Epilachna admirabilis, Aulacophora femoralls, A.nigripennis and A.lewisii which feed on Cucurbitaceae. The former 3 species are stimulated to feed by cucurbitacin, but the latter is not. A feeding stimulant was isolated from a sponge gourd which A.lewisii preferably feeds on. A isolated compound was a kind of steroids. This compound did not act as a feeding stimulant to E..adomirabilis, A.femoralis and A.nigirpennis This compound is a key substance when A.lewisii feeds on a sponge gourd. Trichosanthes kirilowii Maxim. var.japonicapreferably feeds on by. E.admirabilis A.femoralis and A.ninigripennis, but this plant dose not contain cucurbitacines. Feeding stimulants were identified them as a kind of steroids, 2A-diethyl 5 a cholesta-7,22E-dien 3 β-ol and luteolin-7-o-glucoside. Feeding stimulative activity was different from species specify. These results indicate that these substances are key substances when 3 species feed on T.kirilowii Maxim var.japonica. The main host plant of Paridea angulicollis is Gynostema pentaphyllum. A feeding stimulant was isolated from G.pentaphyllum, and was estimated as a kind of triterpenoid glucoside. It is thought that many phytophagous insects are not stimulated to feed by specific substances in the host plants. This investigation may reveale that what kind of substances are used when phytophgous insects feed on host plants not contained specific substances.