THE EFFECTS OF ELEVATED HOST-PLANT CADMIUM AND COPPER ON THE PERFORMANCE OF THE APHID APHIS-FABAE (HOMOPTERA, APHIDIDAE)

1. The uptake patterns of cadmium and copper by the black bean aphid f rom its host-plant Vicia faba, grown under control and elevated metal treatments, were compared. 2. Initial experiments demonstrated signifi cant Cu and Cd accumulation by treated host-plants. 3. Aphids feeding on treated plants accumulated Cd, but not Cu. 4. Concentrations of Cu were significantly higher in the honeydew of aphids feeding on treated plants compared with controls, whereas those of Cd were not. 5. The a phid thus dealt with Cu and Cd in different ways. Copper was primarily excreted in the honeydew and concentrations in body tissues did not i ncrease. Cadmium accumulated within the body and little was excreted i n honeydew. 6. Nine separate experiments, four using Cu and five invol ving Cd treatments, showed little consistent effect of enhanced metal concentrations on several parameters of aphid growth and reproduction. In one Cu experiment, development period to maturity and reproductive rate were significantly enhanced, but the result was not repeatable i n three subsequent experiments. Similarly, significant effects of Cd o n the same parameters were shown in only one experiment out of five. T he high metal concentrations used appeared to have few deleterious eff ects on aphid growth, development and reproduction. 7. Results are dis cussed in the context of trace metal transfer between trophic levels i n polluted ecosystems and the possible main transfer pathways for Cu a nd Cd are identified.