How Hawkmoth Wings Might Sniff Out a Plant to Lay Eggs

Insects have noses on their antennae. That much has been known for a long time. But a new study reveals that the tobacco hawkmoth has been hiding a secret: its wings can smell too. Specifically, they can detect chemical compounds found in the very plants the moth uses to lay its eggs. It adds a surprising new role to what scientists thought wings could do.

Researchers studying the tobacco hawkmoth, known scientifically as Manduca sexta, found that the wings are not just tools for flying. Writing in the Journal of Experimental Biology, the team used a combination of microscopy, electrical recordings, and genetic analysis to show that the wings contain tiny hair-like sensory structures capable of detecting airborne chemicals. Two compounds in particular, pyrrolidine and piperidine, consistently triggered a measurable response from the wings. Both are key chemical building blocks of alkaloids found in the plant family that includes tobacco and moonflowers, which are the hawkmoth’s preferred egg-laying sites.

Put simply: a moth may use its wings to sniff out the right plant to lay its eggs on. It’s an unexpected job for a wing, and one no one had shown in this species until now.

How Hawkmoth Wings Work as Smell Organs

To understand how wings could possibly detect smells, the research team used high-powered scanning electron microscopy to get an extremely close look at the edges of the moth’s wings. What they found were two distinct types of tiny hair-like structures sitting along the wing margins.

One type had a smooth, pointed surface and appeared to be purely mechanical sensors, helping the moth feel its way through the air. The second type was different. These sensory bristles, averaging about 80 micrometers in length, roughly the width of a human hair, had a pitted surface texture and, most important, tiny pores in their walls. In insect biology, pores in sensory structures often point to a chemical-sensing role.

On average, the researchers counted between 21 and 32 of these bristles along the margins of each wing. Female moths had more of them on their hindwings than males did, a detail that may matter, given that females are the ones searching for egg-laying sites.

Identifying the structures was only the first step. To confirm the wings could actually detect odors electrically, the team used a technique adapted from a classic insect-biology method that measures electrical signals in antennae in response to smells. They modified it for wings, calling the adapted method electrowingography.

Hindwings from both male and female moths were attached to recording electrodes, and a continuous stream of filtered air was directed across the wing surface. Then, one by one, 13 different synthetic compounds were puffed across the wing, along with air collected from real plants. Out of all of them, only pyrrolidine and piperidine produced a measurable electrical response. Other chemically similar compounds did not trigger a response, nor did terpenes, esters, or acids. The response also appeared to scale with concentration, with a detection threshold appearing at a dilution of 1 to 1,000.

To pin down where exactly the response was coming from, the team physically cut the margins off the hindwings and repeated the recordings. The trimmed wings still responded. That points to odor-sensitive bristles existing beyond the wing margins, though exactly where they sit is still unknown, possibly tucked beneath the dense layer of wing scales.

Finding the Genetic Fingerprint of Smell

On the genetics side, the team scanned the wing margins for the presence of genes responsible for building smell-detecting and taste-detecting proteins.

Fifteen such genes were actively expressed in the wing margins. Among the most notable were genes for two proteins linked to detecting amines, a class of nitrogen-containing chemical compounds. A separate gene, one that a different family of smell receptors needs in order to work, was missing from the wings. That missing piece belongs to the odorant-receptor system, not the amine-sensing one, so its absence fits the finding that the wings reacted only to amine compounds. Even so, the study did not establish a causal link, and whether the wings can sense other odor classes through some other route remains unknown.

To identify which specific receptor proteins might be doing the work, the team used computer modeling to predict the three-dimensional shapes of candidate proteins and simulated how pyrrolidine and piperidine would physically fit inside them. Two proteins from a related group stood out as computational candidates, meaning their predicted shapes appeared compatible with both active compounds. Each showed a consistent pattern of chemical bonding that used the same key anchor point in its binding pocket. That kind of consistency is a suggestive signal in molecular biology, but these findings are hypotheses generated by simulation, not functional conclusions. The proteins have not yet been confirmed to actually bind pyrrolidine or piperidine; full confirmation would require testing the receptor genes in a living biological expression system.

Why Hawkmoth Wings Matter for Egg-Laying

Pyrrolidine and piperidine are not random chemicals. They are the structural backbones of the alkaloids produced by the plant family that includes tobacco, moonflowers, and related species that hawkmoths preferentially use as egg-laying hosts. The researchers suggest these compounds may not normally drift through the air around undamaged leaves, but could be released when a moth scratches or disturbs a leaf surface while hovering and inspecting a potential egg-laying site.

That detail reframes how the discovery might work in practice. A female hawkmoth hovering in front of a plant, her wings beating rapidly just centimeters from the leaf surface, may be doing more than staying airborne. Her wings could be actively sampling the chemical environment, the authors propose, helping her confirm she has found the right plant.

Researchers also pointed to parallel findings from their own earlier work on hawkmoth legs, where similar receptor types were found to respond to pyrrolidine in a grooming organ on the foreleg. That pattern, the same chemical sensitivity appearing across multiple body parts, suggests the ability is not accidental. Detecting these compounds outside of the antennae may be genuinely important to the moth’s survival and reproduction.

Insect wings have long been studied for how they help animals fly and sense the air around them. For hawkmoths, this research makes a strong case that wings do something more during those critical moments spent hovering in front of a plant, effectively acting as a second nose aimed directly at a potential nursery for the next generation.

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Paper Notes

Limitations

The study has several important constraints worth noting. While the electrical recordings confirmed that wings respond to specific amine compounds, the experiments could not precisely locate which structures on the wing surface beyond the margins were responsible, since removing the margins did not eliminate the response. Structural sensilla were not found on the wing surfaces themselves, possibly because they are concealed beneath the dense covering of wing scales. Additionally, the molecular docking simulations, while suggestive, are computational predictions and not direct experimental proof that the identified receptor proteins bind to pyrrolidine or piperidine. Full functional confirmation would require testing the receptor genes in a living biological expression system. Finally, how odor signals from the wings actually influence the moth’s behavior in real-world conditions remains unknown, as pyrrolidine alone did not trigger feeding or egg-laying behavior in previously reported wind tunnel experiments.

Funding and Disclosures

According to the paper, the study was supported by the Max-Planck-Gesellschaft in Germany, which funded all authors, and by the Ministry of Higher Education and Scientific Research of the Arab Republic of Egypt, which supported one of the authors. Open access publication was funded by the Max-Planck-Gesellschaft. The authors declare no competing or financial interests.

Publication Details

Paper Title: Noses on the wing: the olfactory capacity of hawkmoth wings

Authors: Ahmed Reda Ismaieel, Regina Stieber, Bill S. Hansson, and Sonja Bisch-Knaden

Affiliations: Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Jena, Germany; Entomology Department, Faculty of Science, Ain Shams University, Cairo, Egypt

Journal: Journal of Experimental Biology, Volume 229, Issue 14

DOI: 10.1242/jeb.252047

Publication Year: 2026 (received December 10, 2025; accepted May 29, 2026)