A novel setup for 3D chasing behavior analysis in free flying flies

Abstract

Background: Insects catching prey or mates on the wing perform one of the fastest behaviours observed in nature. Some dipteran flies are aerial acrobats specialized to detect, chase and capture their targets within the blink of an eye. Studies of aerial pursuits and its underlying sensorimotor control have been a long-standing subject of interest in neuroethology research. New method: We designed an actuated dummy target to trigger chasing flights in male blowflies. Our setup generates arbitrary 2D target trajectories in the horizontal plane combining translation up to 1 m/s and angular rotation up to 720°/s. Results: Using stereovision methods we reconstructed target and pursuer positions every 5 ms with a maximum 3D error of 5 mm. The pursuer's body pitch and yaw angles were resolved within an error range of 6deg. An embedded observation point provides a close-up view of the pursuer's final approach and enables us to measure its body roll angle. We observed banked turns and sideslip which have not been reported for chasing blowflies in the past. Comparison with existing method(s): Previous studies focused on pursuit along circular paths or interception of translating targets while our method allows us to generate more complex target trajectories. Measurements of body orientation in earlier accounts were limited to the heading direction while we extended the analysis to include the full body orientation during pursuit. Conclusions: Our setup offers an opportunity to investigate kinematics and governing visual parameters of chasing behaviour in species up to the size of blowflies under a large variety of experimental conditions. ⁎ Corresponding author at: Institut des Sciences du Mouvement, Bât soufflerie -CP 910,

Two pursuit strategies for a single sensorimotor control task in blowfly

“…2c). The preferred direction angle − 21° is an offset due to the definition of the direction of rotation of the target (see 37 ). The length of its mean vector suggests that in the horizontal plane, the fly is using a constant target heading angle controller.…”

“…These sexual dimorphisms support male chasing behaviour and have probably developed under high evolutionary pressure. In the vertical plane, however, we know that the body axis is hardly aligned with the speed vector, nor with the LOS 37 . The role that the orientation of the body plays in the dynamics of the pursuit is the subject of an article in preparation.…”

“…The horizontal angle of error, θ EH tends to be equal to zero since the body axis is usually aligned with the speed vector. In some cases, however, the body axis and speed vector are not aligned, for instance during side-slip-as a result of inertia during high speed banked turns, acrobatic moves during chasing flights 37 , or-more importantly-after sudden body saccades (rotations around the vertical axis) 39 .…”

“…This created an offset for the target heading angle, θ EH = 21°, as presented in Fig. 2c (more details are discussed in 37 ). The θ EH offset, and the maximum head-thorax yaw angle measured in blowflies are very similar.…”

“…Animals. We used a recently developed setup 37 to record chasing flights in blowflies (Lucilia sericata). Pupae were purchased from an animal supplier (BioFlyTech) in Spain.…”