Honey bee signals are primarily studied through natural observation combined with manipulations of the colony or environment, not direct manipulation of the signal stimulus or receivers. Consequently, we know little about which signal aspects are necessary to reproduce behavioral responses. Here, we focus on the shaking signal, wherein a worker grabs onto another bee and vibrates. All castes receive shaking signals, but individual responses depend on context, and the signal may be multi-modal (mechanical, odor, sound, etc.). We designed a tool to mimic the shaking signal. We tested whether a purely mechanical stimulus elicited the same behavioral response as a natural shaking signal, teasing apart the effects of signal and receiver characteristics. We found that both workers and drones increased their movement after being artificially shaken, and that shaken drones were more likely to engage in feeding and grooming than a sham control. These behavioral changes support the idea that the shaking signal serves to generally increase worker activity, but also serves to activate male reproductives (drones). With this tool, we show that vibration itself is responsible for eliciting much of the shaking signal's behavioral response, in one of the few examples of direct playback in social insects.Social insect colonies face the remarkable challenge of coordinating many individuals through decentralized systems to accomplish common goals. Colonies typically have castes or worker groups that perform different tasks, are located in different areas of the nest, and may respond to different stimuli, granting them experience-specific information about the broader colony context 1,2 . Social insects have evolved many signals that communicate specific information between individuals performing the same task 3 . One example is the honey bee waggle dance, which is performed by a forager bee to communicate the location of a good food source to another forager 4 . The honey bee shaking signal, however, is unique because it is used to relay general information to all workers, regardless of the task they are performing 5 . The shaking signal is considered a modulatory communication signal because it does not lead the recipient to change its behavior in a specific way. Instead, it leads to a general increase in activity by the receiver and an increased probability that they will behave in certain ways, depending on their identity 6 .All workers can perform the shaking signal, even workers as young as 2 days old, but the majority of shaking signals are administered by older workers 7,8 . To perform a shaking signal, a worker bee grabs onto a recipient and vibrates at 16.3 ± 5.8 Hz for 1.2 ± 0.3 s 9 . While only workers transmit the shaking signal, all individuals in the colony can be recipients of the signal: workers, drones, and queens 6 . The response, however, varies depending on the recipient 10 . When workers are shaken, they increase their movement, change their trajectories within the nest, and those of foraging-age move to the dan...
