PREDATORY EFFICIENCY OF FRESHWATER BUGS Diplonychus indicus VENK. & RAO (HEMIPTERA: BELOSTOMATIDAE) AND Ranatra filiformis FABRICIUS (HEMIPTERA: NEPIDAE) ON THE LARVAE OF THE DENGUE VECTORS Aedes aegypti LINNAEUS AND Aedes albopictus SKUSE (DIPTERA: CULICIDAE)

Use of biological agents for the control of mosquitoes is of paramount importance owing to its ecofriendly nature. The predatory potential of Diplonychus indicus and Ranatra filiformis was evaluated on the third instar larvae of dengue vectors, Aedes aegypti and Aedes albopictus as prey under laboratory simulated natural conditions for three consecutive days. The predatory impact and clearance rate was calculated, and in addition, the mutual interference constant between predators when present in multiple numbers was also determined from the data pertaining to the clearance rate. The predatory impact values for Diplonychus indicus and Ranatra filiformis against Aedes aegypti ranged from 17.3 to 20.0, and 17.8 to 19.2, and against Aedes albopictus, it was 16.8 to 20.6, and 14.6 to 15.9 respectively. The predatory impact did not vary among the two predator species and the two prey species, and so was the interaction between them too, although it was pintsized higher in Diplonychus indicus. The clearance rate for Diplonychus indicus and Ranatra filiformis against Aedes aegypti ranged from 2.5 to 2.8, and 2.1 to 2.5, while it ranged from 1.2 to 1.8, and 1.4 to 2.0 against Aedes albopictus respectively. The clearance rate values did not vary between the predator species and days, though with pintsized difference on Day 2. Diplonychus indicus and Ranatra filiformis consumed dengue larvae effectively, and the rate of consumption amongst the two predators differed in a miniscule which might be due to the difference in the life history traits and features of the predators, and hence play an important role in the regulation of dengue larval mosquito population.