The secrets of bumblebee reproduction: identifying key pheromones and neural mechanisms

• Applicant: Professor Dr. Thomas Schmitt
• Subject Area: Sensory and Behavioural Biology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 569033645

Insects use specific chemical compounds to signal their reproductive status and attract the opposite sex for mating. However, aside from a few taxa—mainly in Diptera (fruit flies) and Lepidoptera (moths)—insect sexual communication remains poorly understood. This includes the chemical nature of the pheromones as well as the neurobiological mechanisms leading to sexual behaviors. The buff-tailed bumblebee (Bombus terrestris) is a key pollinator in temperate climates. Males produce a pheromone that marks objects along flight paths and attracts both males and virgin queens. While many compounds from the male labial gland have been identified, some remain unknown. Virgin queens also produce a sex pheromone that is actively distributed across their cuticle. Epidermal glands are thought to contribute to this pheromone, but the chemicals involved are still unclear. Consequently, the full range of compounds relevant for sexual attraction, the processes by which they are detected by male and virgin queen bumblebees, as well as how these signals are processed in the brain to elicit sexual behavior, are still poorly known. The Bumble-Date project aims to elucidate how bumblebees utilize sex pheromones for reproduction. First, we will conduct a comprehensive chemical analysis of both male and queen pheromones (WP1). Then, coupling chemical separation and electrophysiological recordings from the insect’s antenna (GC-EAD), we will identify the compounds that are strongly detected by the sexuals compared to workers (WP2). Then, using our knowledge on the neuroanatomy of the bumblebee brain, which will be acquired thanks to immunohistochemical staining, confocal imaging and 3D reconstructions (WP3), we will perform in vivo calcium imaging to study odor-evoked responses to male and queen pheromones in the antennal lobe—the primary olfactory center in the insect brain— in males, queens, and workers (WP4). All along, we will perform behavioral experiments (including both attraction experiments and copulation monitoring) to demonstrate the role of the extracts, as well as of their key components on bumblebee mating behavior (WP5). Altogether, this project will provide a comprehensive understanding of sex pheromone communication in a key pollinator species.

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partner: Professor Dr. Jean-Christophe Sandoz