Cucurbitacins : Plant-derived defense compounds for diabroticites (Coleoptera: Chrysomelidae)

Abstract

Four species of diabroticites with different host specificities are shown for the first time to sequester cucurbitacins. While all beetles fed on an artificial diet (no cucurbitacins) were readily consumed by Chinese praying mantids, a significant proportion of adultDiabrotica balteata (72%),D. undecimpunctata howardi (46%), andD. virgifera virgifera (24%) fed on squash fruit containing cucurbitacins B and D were rejected. Moreover, even when adults did not feed on cucurbitacins, 21-24% ofAcalymma vittatum were rejected by the mantids which is consistent with larval sequestration of cucurbitacins. The mantids failed to learn to avoid any of the beetle species despite adverse effects associated with ingestion, i.e., uncoordination, regurgitation, etc. A cucurbitacin D metabolite accumulated and was sequestered for extended periods of time in the hemolymph of all four species. In addition, female beetles that had ingested cucurbitacins laid eggs containing substantial amounts of cucurbitacins.