A biomonitoring procedure utilizing negative phototaxis of first instar Aedes aegypti larvae

Negative phototaxis of newly hatched Aedes aegypti L. larvae was inhibited by exposure to three heavy metals and five organic insecticides. This response was quantified in an inexpensive multiunit apparatus consisting of four glass troughs perpendicular to a uniform light source. The criterion of toxic effect, established with cupric sulfate as a standard, was: inability of larvae to migrate 30 cm in 60 sec after 8 hr of pre-exposure, designated as 8-hr EC50. The photomigration procedure was more sensitive than our comparative 24-hr acute lethal toxicity tests on metals. The 8-hr EC 50 values for cadmium, chromium and copper were 0.6, 2.4, and 1.4 mg/L, respectively. Values for insecticides ranged from 0.003 mg/L for fenitrothion (organophosphate) to 0.39 mg/L for methomyl (carbamate).