Olfactory reception of the labial palps in Helicoverpa armigera

The olfactory system of insects plays an essential role in their survival and reproduction. In addition to antennae, the maxillary palps of dipteran insects and the labial palps of lepidopteran adults are also important olfactory organs. While the antennae and maxillary palps have been extensively studied, the olfactory function of the labial palps in Lepidoptera remains poorly understood. In this study, we investigated the olfactory capabilities of the labial palps in Helicoverpa armigera, a major global agricultural pest. Electrolabialpalpography screening of 94 odor compounds revealed six compounds that elicited strong electrophysiological responses: N-methylpiperidine, pentylamine, heptylamine, butylamine, propionic acid, and acetic acid. Behavioral assays revealed that N-methylpiperidine and acetic acid acted as strong attractants, while pentylamine, heptylamine, and butylamine exhibited repellent effects. We further demonstrated that the ionotropic receptor HarmIR8a participated in detecting N-methylpiperidine, as HarmIR8a-/- mutants showed significantly reduced responses. Notably, the labial palps, rather than the antennae, were the primary olfactory organs responsible for the attraction to N-methylpiperidine. These findings highlight the specialized role of the labial palps in H. armigera's olfactory system and provide new insights into the sensory mechanisms underlying their behavior. Our results will lend support to the exploration and development of odor-based management tools, such as attractant-based lures or repellent-based push-pull systems, to control H. armigera populations. © 2025 Society of Chemical Industry.