The effect of deterrent compounds in Centaurea maculosa, Spotted Knapweed, on feeding behaviors of Malacosoma americanum, the Eastern Tent Caterpillar.

Abstract

Plants are exposed to many dangers and have evolved toxins and deterrents in response to the threat of herbivory, sometimes resulting in the counteradaptation of insect specialists. Our study examines one specialist, Malacosoma americanum, the eastern tent caterpillar and their feeding behavior with respect to Centaurea maculosa, spotted knapweed, a non-host species that they commonly encounter during dispersal. We created extracts and ran feeding trials to determine if a chemical deterrent exists in kanpweed which prevents the eastern tent caterpillar from consuming it. Data obtained from preference tests with acetone/knapweed extract showed a significant avoidance of extract-coated disks (X2 = 10.70, df = 1, p < 0.001); these results strongly indicate the presence of a polar deterrent compound in knapweed. The caterpillars that did consume some knapweed-coated leaves showed no visible adverse effects, suggesting that the deterrent compound in knapweed may be non-toxic to the eastern tent caterpillar.