Individual flight headings for Drosophila melanogaster in response to different wavelengths of light

Celestial orientation and navigation are performed by many
organisms in contexts as diverse as migration, nest finding and
straight-line orientation. The vinegar fly, Drosophila
melanogaster, performs menotaxis in response to celestial cues
during tethered flight and can disperse more than 10 kmunder
field conditions. However, we still do not understand how spectral
components of celestial cues and pauses in flight impact heading
direction in flies. To assess individual heading, we began by
testing flies in a rotating tether arena using a single green LED
as a stimulus. We found that flies robustly perform menotaxis and
fly straight for at least 20 min. Flies maintain their preferred
heading directions after experiencing a period of darkness or
stopping flight, even up to 2 h, but reset their heading when
the LED changes position, suggesting that flies do not treat this
stimulus as the sun. Next, we assessed the flies’ responses to a
UV spot alone or a paired UV–green stimulus – two dots situated
180 deg apart to simulate the solar and antisolar hemispheres. We
found that flies respond to UV much as they do to green light;
however, when the stimuli are paired, flies adjust for sudden 90
deg movements, performing sun orientation. Lastly, we found no
evidence of a time-compensated sun compass when we moved the
paired stimuli at 15 deg h−1 for 6 h. This study demonstrates
that wavelength influences how flies respond to visual cues
during flight, shaping the interpretation of visual information
to execute an appropriate behavioral response.