Sex and caste effects on the vibrational sensitivity in honey bees (Apis mellifera)

In the darkness of their nests, most social insect species communicate relying on chemical, tactile, electrical and mechanical signals. In honeybees, vibrational signals play a role not only in worker communication but also in communication among virgin queens in the process of swarming. Whereas the sensitivity to vibrations has been well studied in worker bees, vibrational sensitivity of queens and drones has never been investigated. We therefore studied the sensitivity to vibrations comparatively in workers, virgin and laying queens and in drones, focusing on the frequency range mainly used by virgin queens (350–500 Hz). Bees were tested behaviorally for responses to pulses of substrate borne vibrations in arenas placed on vibrational exciters. Vibrational amplitudes were measured using (LDV-calibrated) accelerometers. Real stimuli and sham stimuli were presented in a pseudorandom order. The threshold was defined as the lowest tested amplitude at which significantly more behavioral reactions were shown to real stimuli than to sham stimuli. Workers and virgin queens respond to amplitudes down to 0.25 m/s². The thresholds of laying queens are substantially higher and they respond to minimum amplitudes of 0.55 m/s². Drones show responses to amplitudes down to 0.6 m/s². We conclude that sex and caste have effects on vibrational sensitivity in honeybees: virgin queens are significantly more sensitive than laying queens, indicating that a high sensitivity is crucial for survival during the process of swarming; workers are likewise highly sensitive to execute efficient everyday work; drones are significantly the least sensitive.