Behavioral and neurophysiological responses of experienced vs. naive generalist predators to induced plant volatiles

Arthropod predators use herbivore-induced plant volatiles (HIPVs) as signals of host/prey presence. The behavioral response of predators to an olfactory cue such as HIPVs is a complex process that results from the interaction of innate preferences (i.e., genetically determined) and those that are acquired during the individual’s lifetime (i.e., learned responses). The spined soldier bug, Podisus maculiventris, is a polyphagous biocontrol agent that likely uses HIPVs in its foraging decisions. We hypothesized that P. maculiventris responses to HIPVs are acquired via associative learning, as suggested by theoretical predictions linking natural enemy host range with odor preferences. We combined behavioral bioassays using Y-tube tests with in vivo electrophysiological recordings to compare the response of naïve (i.e., lab reared in colony) vs. experienced (i.e., field collected) individuals to HIPVs such as methyl salicylate to identify the process that drives odor preferences in generalist predators. In preference tests, field-collected predators preferentially oriented toward the scent of caterpillar (Manduca sexta) damaged tomato plants, but lab-reared individuals showed no preference. Thus, stink bug attraction to volatile cues appears to be acquired by learning rather than innate.