Predators may have multiple effects on prey, including the mortality caused by consumption, but also nonconsumptive effects when prey alter their life history traits in the presence of predators. This study aimed to describe the consumption ability and the non-consumptive effects of Notonecta sellata (Heteroptera: Notonectidae) on immature stages of Culex pipiens (Diptera: Culicidae). Results showed that adult N. sellata were capable of preying on all larval instars, although they consumed more individuals of the 2 nd and 3 rd instars. Immature mosquitoes raised in the presence of, but without contact with, predators showed a slower development and smaller-sized emerging adults than those raised in the control treatments. Similar survival rates were recorded in the predator and control treatments. The present study suggests that N. sellata adults negatively affect Cx. pipiens populations in two ways: a) by increasing immature stage mortality as a result of direct consumption and extended development times; and b) by reducing their number of offspring, as a result of delayed reproduction and a lower fecundity of adults. Journal of Vector Ecology 37 (1): 245-251. 2012.

Predaceous larvae of the water scavenger beetle Tropisternus setiger (Germar) are common inhabitants of variable environments in which prey availability may vary widely. We conducted laboratory experiments to assess the effect of prey density on developmental times and survivorship of the preimaginal stages of T. setiger. We also examined the effect of the number of consumed prey on the larval size of instar III. Four different prey densities (one, two, four, and eight preys a day) were tested and both developmental time and survivorship differed significantly among them. Larvae fed one or two preys daily showed a longer developmental time and a lower survivorship than larvae fed four or eight preys a day. Moreover the consumption of four preys a day increased larval developmental success, and to consume one prey a day affected survivorship through the larval period. On the other hand, prey density had no effect on the final larval size.