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A bean aphid, Megoura crassicauda, which feeds selectively on the plant genus Vicia (Fabaceae), was found to be stimulated to probe an extract solution of the host plant, narrowleaf vetch, Vicia angustifolia L., depositing characteristic stylet sheaths on a parafilm membrane. Two acylated flavonol glycosides were isolated as the specific probing stimulants from the extracts and characterized as quercetin 3-O-α-l-arabinopyranosyl-(1→6)-[2″-O-(E)-p-coumaroyl]-β-d-glucopyranoside and quercetin 3-O-α-l-arabinopyranosyl-(1→6)-[2″-O-(E)-p-coumaroyl]-β-d-galactopyranoside. A mixture of these compounds in the same equivalency strongly induced the probing response from M. crassicauda, suggesting their kairomonal roles during host recognition. [Copyright &y& Elsevier]