Development and Survival of Anopheline Immatures (Diptera: Culicidae) in Rice Fields in Northern Thailand1

Abstract

Development and survival of immature anopheline mosquitoes were studied in 4 rice fields in northern Thailand. Adding food to rice-field water shortened the larval duration and increased pupal size of Anopheles peditaeniatus in predatorfree cages. The mean survival of natural populations of Anopheles (Anopheles) (mostly peditaeniatus and sinensis) from larval hatch to adult emergence was estimated to be 2% (range 0–6%) using vertical age-grading methods. Mortality attributable to aquatic predators was variable among fields (19–54%) and was correlated positively with the abundance of aquatic predators (excluding Cyclopoida). Surface predators were a minor mortality factor (0–10%). Nonpredator-related mortality was greater than predator-related mortality in 2 of 4 rice fields. The floating plant Azolla imbricata increased mortality among An. peditaeniatus and An. sinensis larvae in the laboratory.