Influence of density on intraguild predation of aquatic Hemiptera (Heteroptera): implications in biological control of mosquito

The water bugs Diplonychus rusticus (Fabricius) (Heteroptera: Belostomatidae) and Anisops bouvieri (Kirkaldy) (Heteroptera: Notonectidae) co-occur in wetlands sharing mosquito larvae as prey. As a consequence, an asymmetrical intraguild predation (IGP) involving D. rusticus as IG predator and A. bouvieri as IG prey can be possible, the outcome of which may vary with the relative density of interacting species. Based on this proposition density dependent effects on the IG prey and shared prey mortality were assessed in the laboratory using varying numbers of IG predator and shared prey (IV instar Culex quinquefasciatus larva). In contrast to single predator system, mosquito larvae were proportionately less vulnerable to predation in IGP, at low density of shared prey. An increase in density of mosquito decreased the mortality of IG prey (A. bouvieri), but the mean mortality of the IG prey increased with the density of IG predator, in IGP system. Increase in density of mosquito and D. rusticus enhanced risk to predation of mosquito while reducing the mortality of A. bouvieri. Interaction between D. rusticus and A. bouvieri as a part of IGP system provides a possible reason of coexistence of mosquito immature along with predators in wetlands. Biological regulation of mosquitoes may be affected, if appropriate predator numbers are not available in the habitats.