Effect of predation on Anopheles larvae by five sympatric insect families in coastal Kenya.

BACKGROUND & OBJECTIVES The use of insecticides to eliminate mosquito larvae from ground pools may disrupt atural predator-induced control of mosquito larvae. Detrimental effects on predators may be directly from toxicity or by eliminating prey organisms. Identifying the principal predators responsible for mosquito suppression is needed to select non-target indicator species for insecticide studies. In this study, we sought to determine trophic level interactions between predators and immature stages of Anopheles gambiae Giles mosquitoes under experimental conditions in the coastal region of Kenya. METHODS To identify effective predation pattern, a series of prey choice experiments was conducted. The relative abilities of five common species of aquatic insects found in the malaria-endemic coastal region of Kenya were assessed in a series of experiments. Experiments were conducted in semi-field conditions at Jaribuni, near the sites of insect collection. RESULTS In single predator experiments, notonectids consumed most of the mosquito larvae; hydrometrids consumed about half of the mosquito larvae in treatments. Veliids and gerrids had significant, but small effects on larval survivorship. Dytiscids did not have a significant effect on mosquito larvae survivorship. In a two-predator experiment, notonectids significantly decreased survivorship of dytiscids without a change in suppressive effects on mosquito larvae. Of the five common predators evaluated, notonectids were clearly the most voracious consumers of mosquito larvae. The predation pressure on mosquito larvae was not affected by the addition of additional prey items, consisting of small dytiscid beetles. The importance of this notonectid species in coastal Kenya suggests that it would be a valuable non-target indicator species for insecticide studies. Hydrometrids were also efficient at consuming mosquito larvae. INTERPRETATION & CONCLUSION Of the five common predators from the Kenyan coast evaluated in this study, notonectids were the most voracious consumers of immature mosquitoes. Their predation pressure on mosquito larvae was not affected by the addition of additional prey items, consisting of small dytiscid beetles.