Fig. 3: Temporal tuning in superpropulsion and role of surface adhesion from droplet stability and ejection.

a We trim the mechanosensitive hair structures (sensilla) located at the top of the anal stylus to disrupt temporal tuning between the droplet and the stylus. b The maximum speed of the stylus (\({V}_{s}^{-}\)) is higher than in control sharpshooters (two-tailed Whitney-Mann U test, *p = 0.011, n = 5 hairless individuals, n = 5 control individuals). In addition, the calculated frequency ratio f_o/f is lower than the expected frequency ratio in control sharpshooters, whereas the speed ratio λ < 1 indicates a disruption in superpropulsion. c High-speed imaging shows that ejected droplets undergo significant deformation, and take-off occurs after the stylus stops moving. d The mean stylus frequencies f in control sharpshooters lie within a tight window of \({({f}_{o}/f)}^{-1} \sim 0.27-0.35\) (inverse of f_o/f), which falls around peak kinematics and energy transfer at droplet take-off. This matching is disrupted in hairless sharpshooters where associated f are scattered away from that window. e The anal stylus exhibits strong capillary adhesion where excreted droplets remain adhered despite lateral and vertical displacements V_d − V_s ~ 2 cm/s observed during mating calls. f Computational fluid dynamics (CFD) simulations reveal a theoretical limit for droplet ejection of a sessile droplet having a contact angle θ (Supplementary Video II). Sessile droplets with a relatively high contact angle (θ^° > 130) do not take off from the surface of the vibrating plate. Superpropulsion is conserved where λ = V_d/V_s > 1 even if ejection does not occur. Due to adhesion, the maximum speed of the droplet is not equivalent to its ejection speed. Error bars of all data points in this figure represent an average value ± one standard deviation.