Defensive Regurgitation of Allelochemicals Derived From Host Cyanogenesis By Eastern Tent Caterpillars

Abstract

Eastern tent caterpillars regurgitate a droplet of enteric fluid when attacked by predatory ants. In laboratory bioassays, the regurgitated fluid of caterpillars fed cyanogenic young foliage of black cherry was more repellent to ants than was regurgitated fluid of caterpillars fed foliage that was less cyanogenic. Chemical analysis showed that hydrogen cyanide (HCN) and benzaldehyde, produced during host cyanogenesis, were present also in the regurgitated fluid. In bioassays with pure solutions, ants tolerated the odor of HCN but were repelled by benzaldehyde. This evidence indicates that incorporation of host—derived benzaldehyde into regurgitated fluid protects tent caterpillars from ant predation. The use or labile, plant—derived compounds in enteric discharges may be an important, but generally overlooked, insect defense.