Can adults of the New Zealand mosquito Culex pervigilans (Bergorth) detect the presence of a key predator in larval habitats?

Abstract

The influence of predators on mosquito populations may be direct through predation or indirect through sub-lethal responses of adult mosquitoes in life history traits such as oviposition behavior. In New Zealand, the backswimmer, Anisops wakefieldi, is a common predator of mosquito larvae found in temporary and permanent water bodies. We predicted that the New Zealand native mosquito, Culex pervigilans, whose larvae are vulnerable to predation of Anisops, would likely avoid the containers with the presence of Anisops or its kairomone. We established temporary water containers without predators, free-roaming predators, caged predators (which were unable to eat mosquitoes), or containers from which predators were removed immediately prior to the experiment (these containers would have remnant kairomones from the predators). Each treatment with Anisops had predator densities of one, three, or nine Anisops. Contrary to our predictions, when choosing oviposition habitats, Cx. pervigilans appeared to ignore the presence of free-roaming Anisops, caged Anisops, and water with Anisops kairomone. We thus observed no significant differences between the numbers of egg rafts laid by Cx. pervigilans in the different predator treatments nor were the number of egg rafts significantly affected by the density of predators. Rather than the presence of predators, environmental factors including temperature, humidity, and pressure were significantly correlated with mosquito oviposition. These mosquitoes appeared to either ignore the presence of the predator, had no ability to detect the presence of predators, or perhaps the cues from Anisops predators were not sufficiently strong enough to alarm these mosquitoes. We argue that the mosquito has not evolved the ability to detect the presence of these predators while ovipositing.