Khadijeh Madahi - Department of Plant Protection, Faculty of Agriculture, University of Guilan, Rasht, Iran.
Ahad Sahragard - Department of Plant Protection, Faculty of Agriculture, University of Guilan, Rasht, Iran.
Reza Hossieni - Department of Plant Protection, Faculty of Agriculture, University of Guilan, Rasht, Iran.

Life table gives the most comprehensive explanation of the survivorship, development, and reproduction of a population. The life table parameters of an aphidophagous midge, Aphidoletes aphidimyza were studied on different densities (۵, ۱۰, ۲۰, ۴۰, ۶۰, ۸۰) of third instar nymphs of Aphis gossypii as prey in a growth chamber (۲۵ ± ۱ °C, ۷۰ ± ۵% RH and a photoperiod of ۱۶L: ۸D h). The pre-ovipositional period of female A. aphidimyza was reduced as prey density increased with no significant difference. The oviposition period was ۳.۸۳۳ ± ۰.۴۰۱ and ۵.۵ ± ۰.۴۶۳ days in lowest and highest prey density, respectively. Fecundity increased significantly with increasing prey density. The lowest fecundity was obtained at density of ۵ preys/day (۴۹.۶۶۷ ± ۶.۰۵۳ eggs) and the highest was at density of ۸۰ preys/day (۱۰۴.۲۵ ± ۷.۷۸ eggs). Intrinsic rate of increase (rm) ranged from ۰.۱۱۰ ± ۰.۰۱۶ to ۰.۱۶۶ ± ۰.۰۱۴ d-۱ with increasing prey density. Net reproductive rate (R۰) was positively dependent on prey density. The peak reproductive values showed that female aphidophagous midge at ages of ۱۷, ۱۸, ۱۹, ۲۲ and ۲۵ days made the highest contribution to the population when reared on ۵ to ۸۰ preys in a day, respectively. However, mean generation time (T) ranged from ۲۲.۴۲ ± ۰.۵۵ to ۲۴.۴۷ ± ۱.۰۴ days. It was concluded that the increase in the density of third instar nymphs of A. gossypii significantly affected the demographic parameters of A. aphidimyza and it had a better reproductive performance in higher prey densities.

Aphis gossypii, intrinsic rate, prey density, reproductive values, Aphidoletes aphidimyza