Slow movement increases the survivorship of a chemically defended grasshopper in predatory encounters.

Studies on insect defenses have investigated the benefits of noxious chemicals, aposematic coloration, and even gregariousness, but little information exists on the role of slow movement (as opposed to rapid escape movement and the absence of movement). Using the chemically defended, slow-moving lubber grasshopper (Romalea guttata) and the northern leopard frog (Rana pipiens), we investigated the role of slow movement in insect defense. In a five-day experiment, frogs did not learn an aversion to lettuce-fed lubbers; we infer that endogenous deterrent chemicals are not important in lubber defense from frogs. In experiment 2, lubbers moved significantly more slowly than crickets in the presence of frogs held under beakers. In experiment 3, control (i.e., slow-moving) lubbers suffered significantly less predation than motion-induced lubbers, and frogs attacked control lubbers significantly later than they attacked motion-induced lubbers. Hence, slow movement appears to be an important component in enhancing lubber survivorship in frog encounters. This is the first demonstration that the slow movement of an␣aposematic insect increases its survival by failing to release the attack response of certain motion-oriented predators.