Abstract
Females of the pea blue butterfly Lampides boeticus fly to the young flower buds of the yam bean plants Pachyrrhizus erosus and the lablab bean plants Dolichos lablab, and equally lay eggs on them. No damage to the yam bean induced by the butterfly larvae was observed. But the larvae gave serious damage to the lablab bean growing up in the vicinity of the yam bean. Distinct difference of damages between both plants seemed to be caused by the defense mechanism of the yam bean plants using natural toxins. Possible defense principles were isolated and identified as four rotenoids cis-12a-hydroxymunduserone, cis-12a-hydroxyerosone, cis-12a-hydroxyrotenone and rotenone from flower buds, seeds and leaves of the yam bean on the base of the larvicidal toxicity toward the common armyworm Mythimna separata. The activity of each principle was quantitatively evaluated. In addition, the relationships between herbivores and the presence of principles were discussed.
