Delayed hatching as a life-history response to intraguild predation: interspecific variation in predatory mites.

When and why embryos delay hatching in response to predation risk remains poorly understood, particularly across species experiencing different ecological contexts. Predator-induced hatching plasticity allows embryos to adjust hatching timing in response to predator cues, yet interspecific variation in delayed hatching has rarely been examined. Phytoseiid mites provide a useful system because delayed hatching can be induced by mechanical stimuli mimicking predator attacks, and predation risk from cannibalism and intraguild predation (IGP) in the vulnerable larval stage varies among species according to diet specialisation. We compared delayed hatching responses among four phytoseiid mite species differing in cannibalism and diet specialisation by exposing eggs to mechanical stimulation and recording hatching timing with unstimulated controls. Mechanical stimulation induced stronger delayed hatching responses in Neoseiulus californicus (odds ratio = 5.73) and Neoseiulus cucumeris (odds ratio = 7.83), a weaker response in Phytoseiulus persimilis (odds ratio = 3.11), and no detectable response in Typhlodromus bambusae (odds ratio = 0.99). The magnitude of delayed hatching corresponded to interspecific differences in cannibalism and diet specialisation, suggesting that variation in predation risk associated with intraguild interactions shapes hatching timing strategies. These findings support the hypothesis that delayed hatching is an adaptive life-history response to intraguild predation risk and suggest that interspecific variation in hatching plasticity may have important consequences for predator community dynamics and the establishment success of biological control agents.