Dispersion, foraging and cognition in Yellow-legged hornet : towards new management methods

The number of invasive species in the world is constantly increasing. These species could cause economic and ecological problems by destabilising the ecosystems into which they are introduced. In 2004, the Asian hornet, Vespa velutina nigrithorax, was accidentally introduced into France. Since then, this invasive hornet has spread through 11 European countries. More than 30% of the Asian hornet's diet consists of honeybees, which has an impact on pollination and the beekeeping industry. The aim of my thesis was to understand how the Asian hornet disperses and exploits the resources present in its environment to improve existing control methods and propose new ones. To do this, I combined several experimental approaches in the laboratory and in the eld to study both the Asian hornet and non-target species potentially aected by these methods of control (bumblebees, wasps). I was rst interested by the behaviour of hornets. In Chapter 1, I studied the mechanisms that might explain the rapid dispersal ability of the species in Europe. Using a citizen science approach, I demonstrated that Asian hornet foundresses on invasion fronts have wing phenotypes that favour a better dispersal capacity. These traits seem to result from an evolutionary phenomenon called spatial sorting. In Chapter 2, I looked at how hornets use visual and social information to nd food and thus adapt to new environments during their spreading. I showed that hornets learn to recognize food sources using visual signals and that they could modify this learning according to the abundance of resources. I also demonstrated the existence of a social inuence that enables Asian hornets to select food sources already occupied by other hornets and thus potentially increase their foraging eciency. This social attraction to food sites could be used in apiary trapping methods. Based on this work, I explored new methods for reducing the Asian hornet population. In Chap- ter 3, I took part in a developing a tracking system based on the operation of electromagnetic wave radars. I obtained the rst three-dimensional ight trajectories of hornets and carried out an experi- ment demonstrating that the millimeter waves emitted by these radars are not detected by insects. In the future, this new development will allow to track hornet movements and helps to locate nests. In Chapter 4, I assessed the eectiveness of a parasite, Metarhizium robertsii, against the Asian hornet and its potential undesirable eects on non-target species. My results showed a dose eect of M. rob- ertsii on the survival and grooming and/or feeding behaviour of these species. Further work is required to conclude whether this biocontrol method is eective. My work increases our understanding on Asian hornet behaviour and provides solutions for improving methods aiming to reduce pressure on apiaries. The impact of the Asian hornet on wild insect populations is still poorly understood. However, my work on foraging behaviour highlights its potential benecial role as a pollinator. I discuss how, in environments where wild pollinators are de- clining, it might be possible to use the Asian hornet as a pollinator while protecting apiaries from its predatory pressure.