Life at the interface: Interactions of insect sensory systems with physically complex environments

The physical properties of a habitat influence interactions among organisms in many important ways. Habitats at the interface between two media (e.g. air and water) are particularly interesting from a biomechanical perspective, because the nature of such habitats is heavily influenced by the physical properties of the two bulk materials as well as the boundary between them. In the context of two ubiquitous interface habitats (air:sand and air:water), I analyzed important physical properties of these media relevant to the gathering of information by insect sensory systems and the interactions between potential predators and prey. At the air:sand interface, the diameter of sand particles was found to be an important physical parameter affecting the success of antlions in capturing prey. The angles of antlion pits built in sand of different particle size ranges were identical to the angles of repose for those particular particle size ranges. Sandy slopes constructed of finer sand were more likely to interfere with ant locomotion (causing ants to fall) than those constructed from coarser sand. When given a choice between patches of sand varying in particle size, antlions were found to sense and respond to differences in sand particle size by building in patches of finer sand. This sensory ability and behavior is expected to result in more effective pits for prey capture. At the air:water interface, the rate of dissipation of surface waves constrains the ability of water striders to detect and localize the source of a disturbance from a potential predator or prey item. Using a novel and noninvasive technique, the rates of decline in maximum wave amplitude and total energy of disturbances were empirically measured. The detection of emerging adult mosquitoes by water striders was investigated by measuring the predation rate of water striders on these medically important insects. Also, the relative importance of visual vs. mechanosensory cues for avoidance of fish predation by water striders was evaluated by comparing mortality rates of seeing vs. sightless water striders in the presence of fish. Vision was not found to have any discernible influence on the vulnerability of water striders to fish predation.