Oenopia conglobata (L.) and Menochilus sexmaculatus F. are important predators of pistachio psyllid, a key pest of pistachio in Iran, the former indigenous, the latter recently adventive. Aphis gossypii Glover infests understory plants in pistachio orchards and is used by both species as an alternative prey when psyllids are scarce. We 'conditioned' beetles by rearing them for five generations on these prey and their respective host plants (Pistacia vera L. and Curcurbita pepo L.), or on eggs of Ephestia kuehniella (Zeller) as a control, and measured the preferences of female beetles for plant and plant/prey odors in an olfactometer. When conditioned on Ephestia eggs, both species found P. vera odors attractive, but not C. pepo odors. Although both plants became more attractive when infested with prey, O. conglobata preferred pistachio/psyllid odors, whereas M. sexmaculata showed no preference. Whereas conditioning on pistachio/psyllid caused O. conglobata to prefer (unfamiliar) cucumber/aphid odors, its innate preference for the former disappeared when conditioned on cucumber/aphid. In contrast, conditioning on pistachio/psyllid did not alter the innate responses of M. sexmaculata to cucumber/aphid odors, whereas conditioning on pistachio/psyllid caused odors of this complex to be preferred. Thus both species exhibited asymmetric, species-specific, responses to conditioning treatments that reflected both innate recognition of plant/prey odors, and some plasticity as a function of recent dietary history, which in some cases led beetles to prefer the novel (unconditioned) plant/prey complex.
