How to become social - the behavioral underpinnings of phase transition in the desert locust
Department of Collective Behavior
What’s the project about? The desert locust, a form of grasshopper, are notorious plague insects. Swarms of locusts can extend over several hundred square kilometers with up to 80 million individuals per km2, posing severe threats to global food security. However, locusts do not always swarm. When food abounds and population density is low, individuals remain cryptic and sedentary ‘solitary’ grasshoppers. Solitary individuals are green in color, which allows them to hide in the vegetation, and tend to avoid conspecifics. Population upsurges and swarming arise when food scarcity forces locusts to aggregate around limited resources, causing them to transition to a 'gregarious' swarm-forming phenotype. This transition encompasses large physiological and morphological changes: locusts change color from a cryptic green to an aposematic black and yellow pattern, become generalist foragers, modify their posture and start producing aggregation pheromones. Although behavioral and physiological changes associated with crowding have been widely documented, the biological mechanisms mediating the initiation of swarming and collective migrations are yet not well understood.
We will combine classic behavioural assays with virtual reality experiments to uncover when and how collective locust marching emerges. We will use QR tags to continuously monitor the behaviour of solitary locusts during their first exposure to marching bands of gregarious conspecifics over several days. Preliminary findings suggest that, while rapid changes in response to conspecifics can be observed within a few hours, these do not appear sufficient to drive persistent phenotypic changes. Instead, solitary locusts displayed marching-like behaviour only after a few days of crowding. Complementary experiments in virtual reality, where individual locusts are embedded within immersive, responsive, and photorealistic virtual swarms with predefined statistics, provide further insights into how changes in individual interaction maps and kinematics can lead to the formation of coordinated marching events.
Who can apply? The project is open to BSc students
