Functional response of different life stages of Hyperaspis polita feeding on cotton mealybug Phenacoccus solenopsis

The functional response is the most basic form of predator-prey interaction and describes the relationship between the number of prey attacked and the initial prey density. Hyperaspis polita Weise (Col. Coccinellidae) is one of the most important predators of some species of mealybugs and is collected from some parts of Iran especially Khuzestan province. In this research, the functional response of the fourth instar larvae, females and males of this predator to varying densities of female cotton mealybug Phenacoccus solenopsis Tinsley was assessed in a growth chamber (30±1˚C, 65±5% R.H. and photoperiod of 14:10 (L:D) h). A cubic logistic regression between the proportion of prey killed and initial prey densities was performed to determine the shape (Type II or Type III) of functional response. Based on the logistic regression, functional response type II were determined for all predator stages. The attack rate (a), handling time (Th), and theoretical maximum predation rate (T/Th) were estimated using Roger's model to be 0.0196±0.0029 h-1, 3.3262±0.4551 h, and 7.2 prey/d for fourth instar larvae, 0.0131±0.00238 h-1, 3.4765±0.7419 h, and 6.9 prey/d for adult females and 0.0195±0.00528 h, 12.013±0.2624 h-1, and 1.99 prey/d for adult males respectively. According to our results, the fourth instar larvae and the adult females of H. polita can be applied as an effective biological control agent against P. solenopsis.