Effect of adult females' predation risk on oviposition site selection in a water strider

In many egg-laying species, females avoid ovipositing at sites where the predation risk is high. Previous studies have mainly focused on the risk for offspring. The effect of predation risk for the females has been considered in some taxa in which parents spend much time at an oviposition site for parental care or mating (e.g., birds, amphibians). In species in which females do not perform activities other than oviposition at sites, the effect of predation risk for females on oviposition site selection has been rarely investigated. We examined whether the predation risk for ovipositing females affects the decision on oviposition in the water strider Aquarius paludum insularis (Motschulsky) (Heteroptera: Gerridae). Adult A. paludum are preyed upon by a backswimmer, Notonecta triguttata (Motschulsky) (Heteroptera: Notonectidae), but N. triguttata does not prey upon eggs or early instars of A. paludum. We allowed female A. paludum to oviposit under one of three conditions: in presence of N. triguttata, in presence of its chemicals, and in absence of the predator or its cues (control). Female A. paludum less frequently oviposited in presence of N. triguttata than in its absence. Oviposition frequency did not differ between females in presence of chemicals of N. triguttata vs. those in the control. Female A. paludum recognized the predation risk upon themselves from the presence of N. triguttata and avoided ovipositing. This study is the first to directly show that the predation risk upon ovipositing females changes oviposition site selection in species in which the time spent at an oviposition site is short.