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Limitations in breeding source reduction practices, development of insecticide resistance in mosquitoes, and ill effects of chemical controlling methods on human and ecosystem health have motivated Sri Lankan authorities working for dengue control to seek for alternative, ecofriendly, and sustainable approaches for controlling of  Aedes  vectors, to manage dengue epidemics. The present study attempted to investigate the predation efficiency of locally available dragonfly nymphs over  Aedes aegypti  under laboratory conditions, aiming to evaluate the potential of using dragonflies as biocontrol agents against dengue.Methods   Nymphal stages of five locally abundant dragonfly species were collected from different stagnated water bodies in Belihuloya area. After morphological identification, a well grown individual of each species was starved for 12 hours and introduced into a glass tank containing 1L of pond water with 200 larvae (4th instar) of  Aedes aegypti . Number of larvae survived in the tank was enumerated hourly up to 48 hours. In case where >75% of larvae are consumed by dragonfly nymphs, additional  Ae. aegypti  larvae were introduced into such tanks. Experiment was repeated for five times. Same procedure was followed with different stages of growth of the dragonfly nymphs characterized by the highest predation rate. General Linear Model followed by Tukey's pairwise comparison was used for statistical analysis.Results   The predation rates of different dragonfly species varied significantly (p<0.05), whereby  Anax indicus  (110±7.14 per day) indicated the highest, followed by  Pantala flavescens  (54.07±5.15) and  Gynacantha dravida  (49.00±11.89), while  Tholymis tillarga  (23.47±2.48) had the lowest. Further, significant variations in the larval predation were found among different maturity stages (10–20; 25-35; and 35–45 mm in body length) of  Ana. indicus  (p<0.05). Regardless of statistical significance, a relatively higher larvicidal activity was observed at dusk than in dawn.  Conclusion. Ana. indicus , which is characterized by the highest predation rate, and  P. flavescens  that has the widest geographical distribution within Sri Lanka along with a notable predation efficacy could be recommended as potential candidates for field trials in biological control of dengue outbreaks via suppression of  Ae. aegypti  larvae.

Larvicidal Potential of Five Selected Dragonfly Nymphs in Sri Lanka over Aedes aegypti (Linnaeus) Larvae under Laboratory Settings