Laboratory evaluation of predation of Toxorhynchites amboinensis (Diptera:Culicidae) on three mosquito vectors of arboviruses in the Philippines

The spread of arboviral disease in the Province of Cavite, Philippines has resulted to the declaration of state of calamities which has led to higher disease burden and economic costs for the province and its population. With this situation, the use of biological control agents like the naturally occurring non - hematophagous Toxorhynchites species with predatory capacity at its larval stage was explored as an alternative approach to environmentally degrading chemical insecticides. Laboratory assessment of the predatory efficacy of wild type Toxorhynchites amboinensis was done independently against Aedes aegypti, Aedes albopictus, and CuIPY quinquefasciatus prey larvae. Field collected Tx. amboinensis from selected areas of Cavite were reared until adult stage and allowed to oviposit in their rearing cages as a source of test insect. Using similar larval instar for the predator and prey species, predatory larvae were individually exposed to 20 and 40 prey densities in plastic cups. Predatory efficacy test was significantly different between the two prey densities offered. Higher predation rate ranging from 19.5 to 20.4 (48.75-51.00%) was recorded in the predatory larvae exposed to higher prey densities. Analysis of the predatory impact (PI) also revealed significant differences among the larval instars. The 4th instar larva was found to be the most predaceous which contributes a PI value of 19.74 to 20.08 (49.35-50.20%) at higher prey density with an overall PI of 15.75 to 17.68 (39.34-44.20%). The observed compulsive behavior of Tx. amboinensis at the latter part of the 4th larval instar stage can be considered as an additional positive behavior in reducing the larval stages of pest or vector population. This makes Tx. amboinensis a potential biological control agent and a potential component for inclusion in vector management program in the Province of Cavite.