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Timing and intensity of bush cricket predation on egg batches of pine processionary moth: No evidence of population control

Abstract:

Bush crickets (Orthoptera, Tettigoniidae) are known predators of egg batches of the pine processionary moth (Thaumetopoea pityocampa Denis and Schiffermüller, Lepidoptera: Notodontidae), a severe pest in Mediterranean pine woodlands. Bush crickets have been proposed as biological control agents of T. pityocampa populations, although their characteristics as generalist predators suggest that this would be possible only during the low-density phases of the processionary population cycle. We combined observational and experimental approaches aiming to determine the role played by the bush cricket Steropleurus andalusius as a regulator of T. pityocampa. The synchrony of the phenology of T. pityocampa egg batches and the activity of bush crickets was poor, with the activity of bush crickets being longer than the period during which egg batches were available. The predation rate of bush crickets reached 23%, varied in time and space, and was independent of T. pityocampa egg-batch density. There was no relationship between the egg-batch densities and bush cricket abundance, and no response to experimental variations in egg-batch density. Analysis of microhabitat selection suggests that T. pityocampa egg-batch predation is a by-product of the substrate selected by bush crickets for mating, and does not correspond with active searching of egg batches as food. These findings do not rule out the possibilty of bush crickets being natural regulators of T. pityocampa populations, although they impose limits with respect to their future use in biological control. © 2013 The Royal Entomological Society.