Social modulation of stinging behaviour in honeybees

Honeybees defend their nest against large predators thanks to a collective effort to harass and sting the intruder. The stinger apparatus has evolved to detach upon stinging elastic skin (such as ours) to maximize venom delivery, but the drawback is that the mutilated bee will then die within a few hours. Thus, the honeybee colony under threat has to achieve a delicate balance: enough bees need to respond that the intruder is successfully deterred, but without unnecessarily depleting the colony of its workforce. What are the mechanisms regulating the decision of each individual to engage or not into this collective response, so that this balance is reached? We propose that honeybees integrate information about the behaviour of their nestmates (social feedback) to fine tune their own response. The aim of this project is to study both the behavioural and the neurobiological bases of this regulatory mechanism.

(Graphic design: https://miriamstepper.com)

Theoretical evolution of the collective defensive response of honeybees

with Prof. Hans Briegel - Theoretical Physics, University of Innsbruck and Prof. Thomas Müller - Philosophy, University of Konstanz

Honeybee societies are characterized by reproductive division of labour, whereby only the queen (and the males) produce offspring while the rest of the colony is composed of sterile workers. This system makes it particularly challenging to understand how evolutionary pressures may act to shape the behavioural responses exhibited by individual workers, especially this response is itself part of a collective effort. This project makes use of a machine learning algorithm called Projective Simulation to better understand the adaptive responses of individual bees during a defensive event. This framework allows for a realistic encoding of the sensory apparatus and motor abilities of the agents, which can perceive, make decisions and act as individuals. When interacting with other agents, their actions may influence the perceptions and responses of the rest of the ensemble, which in turn leads to the emergence of collective behaviour. Importantly, agents can learn about appropriate actions to take in a given environment through a reinforcement learning scheme, which in our case emulates natural selection. 

(Photo: Africanized honeybee (left) and European honeybee (right). These two subspecies differ widely in their aggressive behaviour. Note that the difference in colour is coincidental, normally they cannot be distinguished by eye. By Scott Bauer, via Wikimedia Commons.)

Impact of glyphosate on bumblebee learning 

with Dr. Anja Weidenmüller - Biology, University of Konstanz 

Glyphosate is the most widely used herbicide in the world. It is sprayed in fields and can remain in the soil for months. Although its toxicity on animals is low, sublethal effects have been reported in a range of species, especially in invertebrates. Bumblebees nest underground, often in abandoned rodent burrows, and forage on flowers. Thus, they are likely to be chronically exposed to glyphosate. Bumblebees are important wild pollinators, but their populations have been declining throughout Europe and North America. Does glyphosate contribute to this decline? The ability to learn which flowers are rewarding is necessary for bumblebees to forage efficiently, and hence for the colony to survive and strive. This is why, in this project, we explore the impact of glyphosate exposure on visual learning by bumblebees. 

(Photo by Sinje Tigges)