Hornet alarm signals reveal individual colony identity and worker differences

Jenn Hoskins
3rd February, 2026

Hornet alarm signals reveal individual colony identity and worker differences

Yellow-legged hornet (Vespa velutina nigrithorax)

Photographer: Piermario Maculan

Key Findings

  • This study, conducted in France on yellow-legged hornets, found variations in alarm pheromone chemicals between different hornet colonies
  • Hornet workers exhibited unique alarm pheromone compositions based on their specific job within the colony—foraging, building, defending, or material gathering
  • Five specific chemical compounds were identified as key markers, distinguishing animal foragers and builders from other worker types
The survival of eusocial insects – those living in highly organised colonies like bees, ants, and wasps – relies heavily on communication, and a key part of this communication is through pheromones, chemical signals used to trigger specific behaviours. Alarm pheromones are particularly important, alerting nestmates to danger and initiating defensive responses. Understanding these signals is crucial for managing invasive species and protecting ecosystems. Recent research from CNRS, University of Tours[1], has investigated the alarm pheromone of the invasive Yellow-legged hornet, Vespa velutina nigrithorax, revealing a surprising level of complexity in its chemical composition. The study focused on identifying variations in the alarm pheromone produced by worker hornets from different colonies and, crucially, how the pheromone differed depending on the specific job the worker was performing within the colony. The researchers examined four worker activities: foraging for animals, building nests, defending the colony, and foraging for materials. The core finding was that alarm pheromones weren’t uniform; significant chemical differences existed between colonies, indicating a unique “chemical signature” for each. Furthermore, the pheromone composition also changed depending on the worker’s role. This research builds upon earlier work demonstrating the complexity of pheromone communication in social insects. For example, studies on termites, Odontotermes formosanus[2], have shown that even with just two pheromone components, termites can convey surprisingly detailed information by altering the ratio of these components. Unlike many insects where pheromone ratios are fixed, O. formosanus dynamically adjusts these ratios based on behaviour, allowing for more nuanced communication within the colony. The V. velutina study suggests a similar principle may be at play, but with a far greater number of chemical compounds involved. The researchers employed gas chromatography coupled with electroantennographic detection (GC-EAD) to identify the compounds that triggered responses in the hornets’ antennae. This technique separates the various chemicals in the venom and identifies which ones the hornets are able to detect. They found that animal foragers and builders had distinctly different pheromone profiles, with specific compounds being unique to each group. This suggests that these pheromones could serve as a recognition signal, not only between different colonies but also between different roles within a single colony. Interestingly, this finding contrasts with some other social insects where alarm pheromones are more consistent across the colony. However, it aligns with observations in ants[3], where chemical signals are often complex mixtures, varying in both the types of compounds and their relative proportions. These variations allow ants to identify different groups and trigger specific actions at various levels of organisation within the colony. The V. velutina study suggests hornets may have evolved a similar system, using a diverse chemical “language” to coordinate complex tasks. Previous research on honeybees also highlights the importance of pheromone detection and response. Studies have shown that Apis cerana bees can eavesdrop on alarm pheromones from other species[4], avoiding areas where danger is present. Furthermore, the sensitivity to specific compounds, like isopentyl acetate (IPA) and gamma-octanoic lactone (GOL), is influenced by both the abundance and volatility of the signal. The findings from V. velutina could potentially explain why certain hornets are more sensitive to specific compounds in the alarm pheromone, depending on their role and the surrounding environment. The identification of specific compounds in the V. velutina venom, including monoketones and diketones, is also relevant to understanding alarm pheromone evolution. Research on Vespa velutina itself[5] has already shown that sting venom acts as an alarm pheromone, with certain compounds triggering attacks. This new study expands on this by demonstrating the chemical heterogeneity within the venom and the link between pheromone composition and worker activity. Identifying the key alarm releasers, particularly at biologically relevant concentrations, remains an ongoing challenge, as highlighted in[5], but the findings from provide a crucial step forward.

BiochemEcologyAnimal Science

References

Main Study

1) Colonial signature of the alarm pheromone and chemical differences between hornet workers

Published 2nd February, 2026

https://doi.org/10.1371/journal.pone.0336261

Related Studies

2) Trail communication regulated by two trail pheromone components in the fungus-growing termite Odontotermes formosanus (Shiraki).

https://doi.org/10.1371/journal.pone.0090906

3) The chemistry of social regulation: multicomponent signals in ant societies.

Journal: Proceedings of the National Academy of Sciences of the United States of America, Issue: Vol 92, Issue 1, Jan 1995

4) Bees eavesdrop upon informative and persistent signal compounds in alarm pheromones.

https://doi.org/10.1038/srep25693

5) Poison and alarm: the Asian hornet Vespa velutina uses sting venom volatiles as an alarm pheromone.

https://doi.org/10.1242/jeb.148783


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