Functional response of the ladybird, Cydonia vicina nilotica to cowpea aphid, Aphis craccivora in the laboratory

The functional response of Cydonia vicina nilotica Muls. （Coleoptera： Coccinellidae） to six densities of Aphis craccivora Koch （Homoptera： Aphididae） nymphs on broad bean （Viciafaba Linn.） was investigated in the laboratory. A linear relationship between the rate of consumption and prey density was observed with r^2 values between 0.58 and 0.97. Plotting prey density against prey killed by four larval instars, and adult males and females of C. vicina nilotica fit well with the type Ⅱ model of Holling＇ s disc equation. Adult females consumed the highest number of prey, followed by fourth instars and adult males. Based on the functional response data, the model predicts a maximum of 144.9, 116.3, 86.2, 80.0, 72.5 and 20.0 nymphs to be consumed per day by an individual adult female, fourth instar, adult male, third, second and first instars, respectively. The differences in the responses of the predator to aphid densities are discussed.