Squash Beetle Feeding Behavior: An Adaptation against Induced Cucurbit Defenses

This study tests the hypothesis that feeding behavior in the herbivorous coccinellid Epilachna borealis is an effective adaptation for avoiding facultative chemical defenses in its cucurbit host plants. Chemical analyses, feeding preference tests, fitness evaluations, and cucumber beetle assays for cucurbitacins show that (1) beetle feeding damage to zucchini leaves triggers chemical change in damaged leaves and leaves adjacent to damaged leaves; (2) this change in leaf chemistry is sufficiently potent for beetles to detect and avoid; (3) induced changes in leaf chemistry negatively affect E. borealis fitness; (4) E. borealis trenching behavior blocks, at least temporarily, the translocation of cucurbitacin defenses to feeding sites, thus preserving the palatability and quality of food resources for beetles.