Jordan Journal of Biological sciences 3(1): 17-20, 2010

Functional response of the predator Hippodamia variegata (Goeze) (Col., Coccinellidae) feeding on the aphid Brachycaudus helichrysi (Kaltenbach) infesting chrysanthemum in the laboratory

Abstract: Functional response of the predatory coccinellid Hippodamia variegata (Goeze) to the density of Brachycaudus helichrysi (Kaltenbach) aphid infesting chrysanthemum was studied under laboratory conditions at 25 ˚C. A single adult female predator on isolated areas with different prey densities was used. Response pattern of the six-day old predator to the various prey densities was found. Predator exhibited a decelerating curvilinear rise to a plateau (type II) response in which the proportion of prey consumed declines monotonically with the initial number of prey offered. The mortality curve of the prey at different densities due to the predator was also evaluated. The mortality first increases with prey increasing density, and then declines. The predator functional response can be simulated by Holling disc equation and expressed as: (Ha = 0.97525 H / 1 + 0.0066317 H) and by the reciprocal linear transformation of Holling’s equation as: (y = 0.5127 x + 0.0068). The estimated coefficient of attack rate (a) is 1.9505 and the handling time (Th) is 0.0034.