D3209: Drosophila suzukii navigate to maintain a stable flight heading relative to celestial cues

How small insects move at a landscape scale is not well understood, although knowledge of this dispersal is essential for managing pests and disease vectors. It is commonly assumed that tiny insects, such as fruit flies, fly around randomly with minimal active dispersal. However, recent mark-and-recapture studies found that Drosophila melanogaster can disperse on straight headings radially at speeds exceeding 1 km/hour. To understand how this dispersal capacity extends to other fruit fly species, we used a virtual reality flight arena to investigate visually-guided navigation in the invasive pest species Drosophila suzukii. We performed automated analysis of high-resolution infrared video to track the wing movements of rigidly-tethered, flying flies, in which continuously measured right-left differences in fly wing stroke amplitude controlled the rotational velocity of an LED stimulus mimicking the sun. In this flight arena, flies actively maintained a straight heading relative to the sun stimulus for extended flights of 10 minutes and longer. Distinct individuals exhibited variability in their heading preference relative to the sun stimulus, indicating an ability to navigate at arbitrary headings. Drosophila suzukii exhibited a similar capacity for straight-line navigation in a distinct arena, in which magnetically-tethered flies turned freely while flying to orient to a sun stimulus. Taken together, these data indicate D. suzukii have a capacity for extended straight-line navigation relative to celestial visual cues. This type of navigation in free flight could result in dispersal distances of multiple kilometers over several hours.