Meeting Abstract
In order to navigate effectively in three dimensions, flying insects must gauge distances to objects around them. Humans use a variety of visual cues that provide information for estimating depth, however, insects are constrained to a reduced range of possible depth cues due to their smaller size and fixed eyes. Flying fruit flies are able to use motion parallax to gauge relative distances of nearby objects, but motion parallax becomes less viable of a strategy across longer distances. For humans, a useful method of estimating depth across longer distances makes use of the horizon; an object that appears closer to the horizon is presumed to be far away. We set out to determine if flying fruit flies, like humans, gauge objects that are near the horizon as farther off. Tethered flies respond strongly to moving objects that they perceive as close, thus we measured responses while varying the apparent elevation of virtual objects in a virtual environment. We found wide-field responses are unaffected by relative horizon elevation, but responses to vertical bars are strongly increased by reducing the apparent elevation of the bar against a virtual horizon. This strong response could indicate that fruit flies are able to assess the distance of far off objects in the natural world by comparing them against the salient natural horizon.
