Olfactory-mediated chemotaxis toward a key host plant leaf volatile in the fall webworm.

BACKGROUND Olfaction is essential for the survival and reproductive success of insects, mediating critical behaviors such as host plant location, mating, and oviposition. The fall webworm, Hyphantria cunea, is a highly polyphagous and invasive pest that infests a wide range of deciduous trees and shrubs. Its ability to efficiently locate suitable host plants primarily guided by olfactory cues, particularly during the larval stage, is a major contributor to its ecological success. While previous studies have examined the general olfactory and gustatory systems of H. cunea, the specific volatile compounds that elicit larval chemotactic responses remain largely uncharacterized. RESULT Behavioral and electrophysiological assays identified that the host plant volatile cis-3-hexenyl acetate (Z3HAc) functions as a chemoattractant for H. cunea larvae. Quantitative real-time polymerase chain reaction (PCR) and calcium imaging revealed that the antennal receptor HcOr3 is highly expressed and selectively responsive to Z3HAc. RNA interference-mediated knockdown of HcOr3 significantly reduced larval attraction to Z3HAc. Furthermore, single sensillum recordings confirmed that HcOr3 knockdown markedly decreased antennal sensitivity to Z3HAc, establishing its critical role in detecting this volatile compound. CONCLUSION We identified Z3HAc as a key attractant in host plants for H. cunea larvae and demonstrated that the receptor HcOr3 likely mediates host plant recognition. This work enhances our understanding of the molecular basis of host-seeking behavior in this invasive pest and highlights HcOr3 as a promising target for species-specific pest control. Our findings elucidate the link between olfactory perception and chemotactic response to natural plant volatiles in folivorous insects. © 2025 Society of Chemical Industry.