Predation rates of mixed instar Odonata naiads feeding on Aedes aegypti and Armigeres moultoni (Diptera: Culicidae) larvae

Abstract

In Thailand, several important diseases are transmitted by mosquitoes. Many vector control programs focus on the reduction of these medically important mosquitoes through the application of pesticides, bed-nets and the introduction of biological control agents. Odonates naiads are important, naturally occurring predators of vector mosquitoes. To estimate the predation rates of odonate species in Thailand, we conducted an experiment in which the predation rates were compared across a range of predator and prey densities. We used seven different predator species from different instars that represented the composition of naiads in our study area. Body sizes ranged between 2.6mm and 15.9mm. Two different prey species were used, larvae of the mosquito Armigeres moultoni Edwards, 1914 and Aedes aegypti L. 1762. Predation rates showed a positive non-linear relationship with prey densities and a negative non-linear relationship with predator densities. The mean±SE predation rates per predator were 6.2±0.8 individuals per 24h for dragonfly naiads and 5.1±0.7 for damselfly naiads. Predation rates were very low compared to previously recorded rates. However, unlike previous research, we did not focus on single species in a late stage of development but on multiple species in all stages that resembled the natural odonata community composition.