Surface tension is not fixed; it drops with temperature, rises modestly with salinity, and plummets when surfactants spread across the interface. For spiders that hover near the capillary limit, a 10 deg C increase can trim gamma by 2-3%, which slightly lowers the capillary length and shrinks the allowable footprint. Brackish water offers a small buffer because gamma increases, but dissolved organics can undo that gain.
Behavior follows these shifts. Field observations note shorter stride lengths on warm afternoons, consistent with legs needing to distribute load more evenly. After a prey event leaves lipid residue, spiders often groom their tarsi to restore the wax layer and avoid Marangoni-driven drifts that would otherwise pull them off course.
Designers should measure gamma and contamination levels before testing prototypes. A quick du Nouy ring or pendant-drop measurement can inform gait parameters: reduce impulse when gamma dips, widen stance when biofilms form, and schedule cleaning cycles to strip surfactants from contact points. Treating environment as a control input keeps performance predictable instead of relying on nominal lab conditions.