Figure 1 |. Drosophila are attracted to ethanol and CO₂ in flight.

a, Diagram of wind tunnel. b, Photograph of the wind tunnel and odor-emitting landing platform. c, d Heat-maps indicating relative occupancy of flies in the presence of either CO₂ or ethanol. Cohorts of 12 flies were introduced into the wind tunnel and their behavior recorded over 16 hrs. Throughout the experiment, 100 mL min⁻¹ of clean air emerged from both odor ports. For 30 min every hour, 60 mL min⁻¹ of either CO₂ or clean air bubbled through 100% ethanol, was added to one odor port. Control data come from segments with clean air. Number of cohorts: 9 (CO₂), 6 (ethanol). Number of trajectories: 59,970 – 101,539 per panel. e, Percent of trajectories that passed through one of the colored volumes shown in c (gold, cyan, green) after also passing through a control volume (white or gold). Approaches to landing pad: gold-from-white; landings: cyan-from-gold; approaches to dark spot: green-from-white. Number of trajectories per condition: 44–1288 (control), 228–1815 (odor). Experiments were performed at two concentrations: 15 mL min⁻¹ (left data) and 60 mL min⁻¹ (right data). Letters above data indicate statistically significant groups (2-tailed Mann-Whitney U test at p<0.05 with 8-way Bonferoni corrections). In all panels, shading indicates bootstrapped 95% CI around the mean.