Effects of predator starvation on oviposition site selection of two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae)

Animals select oviposition sites to reduce predation risk for their offspring. Generally, predation risk increases with predator starvation. When predators become more dangerous to prey by starvation, prey should avoid oviposition on patches with starved predators compared with satiated predators. We tested this possibility using herbivorous mites, Tetranychus urticae Koch (Acari: Tetranychidae), and two predatory mite species, Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae) and Neoseiulus californicus (McGregor) (Acari: Phytoseiidae), focusing the role of predatory mite cues in the absence of predatory mite themselves. Adult female P. persimilis and N. californicus that had been starved for 1 or 3 days consumed more T. urticae eggs than satiated conspecifics, irrespective of the starvation duration. This suggests that both predators become more dangerous to T. urticae eggs after having been starved. Subsequently, we offered adult female T. urticae choice between a clean leaf patch or a leaf patch exposed to P. persimilis or N. californicus that had been satiated or starved for 1 or 3 days. Adult female T. urticae laid more eggs on the clean patches in the presence of satiated predator cues than starved predator cues, irrespective of the predator species and starvation duration. These results suggest that adult female T. urticae were less likely to decrease the predation risk to their offspring based on starvation levels of predators. This incomplete predator avoidance may facilitate the coexistence of predators and prey.