How Wasps Acquire and Use Views for Homing

Abstract

Nesting insects perform learning flights to establish a visual representation of the nest environment that allows them to subsequently return to the nest. It has remained unclear when insects learn what during these flights, what determines their overall structure, and, in particular, how what is learned is used to guide an insect's return. We analyzed learning flights in ground-nesting wasps (Sphecidae: Cerceris australis) using synchronized high-speed cameras to determine 3D head position and orientation. Wasps move along arcs centered on the nest entrance, whereby rapid changes in gaze assure that the nest is seen at lateral positions in the left or the right visual field. Between saccades, the wasps translate along arc segments around the nest while keeping gaze fixed. We reconstructed panoramic views along the paths of learning and homing wasps to test specific predictions about what wasps learn during their learning flights and how they use this information to guide their return. Our evidence suggests that wasps monitor changing views during learning flights and use the differences they experience relative to previously encountered views to decide when to begin a new arc. Upon encountering learned views, homing wasps move left or right, depending on the nest direction associated with that view, and in addition appear to be guided by features on the ground close to the nest. We test our predictions on how wasps use views for homing by simulating homing flights of a virtual wasp guided by views rendered in a 3D model of a natural wasp environment.

Keywords: Cerceris; insect navigation; learning flights; visual homing; wasps.