Sexual dimorphisms of the olfactory system are conserved across bumblebee species

Bumblebees are integral to ecosystems as crucial pollinators. However, neuroscience has kept its focus on studying workers of commercially available species: Bombus terrestris (Europe), B . impatiens (North America), and B . ignitus (Asia). Here, we conducted a detailed comparative study of the brain and antennal anatomy in wild worker and male bumblebees of 6 common European species ( B. terrestris , B. pascuorum , B. pratorum , B. lapidarius , B. hypnorum , and B. lucorum ), with specific focus on their peripheral and central olfactory system. We found striking sexual dimorphisms that remain consistent across species and may underlie the differences in foraging preferences in bumblebees. We also developed a bespoke machine learning-based pipeline for automatic segmentation of confocal images of antennal lobes, which greatly speeds up the image analysis.