Squash beetle trenching behaviour: avoidance of cucurbitacin induction or mucilaginous plant sap?

Publisher Website
Google Scholar
Abstract
Foraging patterns of the squash beetle, Epilachna borealis Fabricius (Coleoptera: Coccinellidae), in field cages are not consistent with the hypothesis that this beetle avoids leaves in which its feeding damage has caused the induction of cucurbitacins. E.borealis feeding does not induce accumulation of cucurbitacins inside or outside of feeding trenches. Cucurbitacins do not reduce the survival or growth rate of E. borealis larvae. High concentrations of cucurbitacins fail to deter E.borealis feeding; rather, cucurbitacins are feeding stimulants for squash beetles. Trenching behaviour in E.borealis is facultative and correlates with leaf turgor and the degree to which sticky phloem sap oozes from damaged leaves. Mucilaginous phloem sap in many curcurbit species inhibits feeding by E.borealis when it is applied to beetle mouthparts.