Hyperaspis polita Weise is the major predator of Phenacoccus solenopsis Tinsley in southwestern Iran. The functional response of fourth instar larva, adult female and male of the ladybird, H. polita, preying upon different stages of the mealybug P. solenopsis was evaluated. All stages of H. polita exhibited type II functional responses against all stages of P. solenopsis with an exception that the functional response of the adult female stage of H. polita to first instar P. solenopsis nymphs was type III. Changing prey and predator stages did not result in significant differences in attack rates. Handling times, however, differed for different prey and predator stages. This parameter was the shortest for any stage of predator fed on first instar P. solenopsis nymphs and was estimated to be 0.1100, 0.1868, and 0.2939 h for fourth instar larval stage, adult females and males, respectively. Also, the handling time was the shortest for the fourth instar larval stage followed by adult females and males to different prey stages. Maximum predation rate (T/Th) decreased as P. solenopsis developed from one life stage to another, the lowest estimated value being obtained by feeding on adult female mealybug and the fourth instar larval stage was the most predatory. According to these results, the feeding potential of H. polita is noticeable with the fourth larval instar stage being considered the most efficient predatory stage for use in biological control programs. Further field-based studies are needed, however, before a comprehensive estimation of the biocontrol abilities of H. polita toward P. solenopsis can be made.
Keywords: Attack rate; handling time; prey density; species invasion; stage dependence.