[Relationships of Aulacophora beetles feeding behavior with cucurbitacin types in host crops]

Aulacophora fermoralis chinensis and Aulacophora cattigarensis are the two related Aulacophora beetles, but their host selectivity and feeding behavior are significantly different. A. fernzoralis chinensis usually feeds upon Cucumis sativus and Cucurbita moschata, but never upon Luffa acutangula, Momordica charantia and Citrullas lanatus. Its feeding behavior on hosts is to snip a circular trench on their leaves, and then, to feed the leaf tissues isolated by the trench. On the contrary, A. cattigarensis only feeds L. acutangula, and its trenching behavior rarely occurs. This study showed that the host selectivity and feeding behavior of the two beetles were significantly correlated with the types of cucurbitacin biosynthesized by host melon crops. C. sativus and C. moschata might be induced to produce cucurbitacin I by A. fermoralis chinensis feeding, and this compound was responsible for feeding deterrent on A. fermoralis chinensis. Therefore, the feeding behavior of A. fermoralis chinensis was to block the translocation of cucurbitacin I to feeding sites. M. charantia and C. lanatus contained deterrent cucurbitacin D, and thus, both beetles never fed upon them, while L. acutangula contained stimulants cucurbitacin B and E, and made A. cattigarensis directly feed upon it without trenching. The results suggested that the taste responses of insects on specific allelochemicals from plants may play an important role in host selectivity and feeding behavior.