Perception of predation risk by caterpillars

Assessment of predation risk and appropriate defensive responses are critical for most organisms. Prey individuals must discern among the cues produced by abiotic factors, competitors and predators and between different types of predators to distinguish among them and respond appropriately. However, the degree to which invertebrate prey species perceive and distinguish these cues, as well as the nature of the signals involved in predation risk assessment is poorly known for most systems. This study examines the signals involved in predation risk assessment by two caterpillars, Semiothisa aemulataria , a caterpillar that that mimics plant parts and a hairy caterpillar Orgyia leucostigma. The predators included two active foraging invertebrate predators which detect prey items at close distances (Podisus maculiventris and Polistes fuscatus), one sit-and-wait invertebrate predator (Sinea diadema), and one visually hunting predator (Pares bicolor).; In Chapter one I tested the hypotheses that: (a) prey respond to signals specifically produced by predators and (b) the signals produced by predators provide the basis for an assessment of the type of predation risk. The results show that using substrate-borne vibrations, larvae of S. aemulataria are able to distinguish between predators, herbivores, and abiotic factors and respond appropriately. Using substrate-borne vibrations, S. aemulataria distinguishes and responds differently to different types of predator threats based on the nature of their foraging and its responses enhance survivorship.; In Chapter two I tested the hypotheses that (a) antipredator behaviors are effective against predators with particular foraging behaviors and (b) morphology and behavior are linked and coordinated to maximize the effectiveness of responses to predation risk. The results show that O. leucostigma responds to the attack by predators during physical contact and different rates of displacement of its defensive hairs generated by predators with different attack modes elicit different defensive behaviors.; The results of this study show that the determination of the outcome of predator-prey interactions may rely less on the taxa or taxa specific traits of the interacting organisms and more on the type of foraging mode of the predator in relation to the sensory capability of the prey.