Predatory mites protect own eggs against predators

Predators frequently compete with other species for prey but can also interact by preying on each other’s vulnerable stages. Because eggs and juveniles are more vulnerable to this intraguild predation than adults, their survival will depend on maternal strategies to reduce predation risk. Recently, we reported that adult female predatory mites Gynaeseius liturivorus Ehara (Acari: Phytoseiidae) reduce intraguild predation on their eggs by remaining at oviposition sites, thus deterring the egg predators. In addition, they avoid oviposition close to eggs laid by conspecific females. We therefore expected that adult female G. liturivorus protect their own eggs better against these egg predators than eggs of other females. This was tested using juveniles of the predatory mite Neoseiulus californicus McGregor (Acari: Phytoseiidae) as egg predators and the western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), as the shared prey. When G. liturivorus eggs were kept with their mothers, the presence of juvenile egg predators did not affect the survival of eggs. However, when G. liturivorus eggs were kept with females that were not their mothers, the mortality of eggs in the presence of juvenile egg predators increased. When adult female G. liturivorus were guarding their eggs, they killed a similar number of juvenile egg predators as females that were not kept with their eggs. Hence, adult female G. liturivorus protect their eggs by remaining close to their eggs.