This deforms the water surface and generates capillary forces that propels the insect up the slope without moving its appendages. Hu and Bush conclude that meniscus climbing is an unusual means of propulsion in that the insect propels itself in a quasi-static configuration, without moving its appendages. Biolocomotion is generally characterized by the transfer of muscular strain energy to the kinetic and gravitational potential energy of the creature, and the kinetic energy of the suspending fluid. In contrast, meniscus climbing has a different energy pathway: by deforming the free surface, the insect converts muscular strain to the surface energy that powers its ascent. Marangoni propulsion Many insects, including some terrestrial insects, can release a surfactant and propel themselves using the Marangoni effect. Hu and Bush report that Microvelia can attain a peak speed of 17 cm/s, which is twice its peak walking speed, using Marangoni propulsion. Marangoni propulsion by a wetting arthropod is precisely analogous to a soap boat but the situation for insects such as water striders is more complex. Hu and Bush state that "for nonwetting arthropods, the transfer of chemical to kinetic energy is more subtle, as the Marangoni stress must be communicated across the creature’s complex surface layer". Sailing Velella, the by-the-wind sailor, is a cnidarian with no means of propulsion other than sailing. A small rigid sail projects into the air and catches the wind. Velella sails always align along the direction of the wind where the sail may act as an aerofoil, so that the animals tend to sail downwind at a small angle to the wind. See also Robostrider Stone skipping References John W. M. Bush and David L. Hu. WALKING ON WATER: Biolocomotion at the Interface. Annual Review of Fluid Mechanics, vol. 38, p. 339-369, January 2006. External links Meniscus-Climbing Insects (photos) Animal locomotion Water transport