A comparative study on the population growth parameters of Coccinella septempunctata (Col.: Coccinellidae) and melon aphid, Aphis gossypii (Hem.: Aphididae) under laboratory conditions

Adult individuals of the ladybird, Coccinella septempunctata L., and also the melon aphid, Aphis gossypii Glover, were collected from cucumber fields in Rasht area, north of Iran. They were reared in a growth chamber at 26  2˚C, R.H. of 65  5% and a photoperiod of 16L: 8D. Ten mated pairs of two-day-old predators were separately transferred in to a plastic container (8 × 10 × 12 cm) that were covered with an organdy net. A demographic life table was constructed based on the daily fertility results. The intrinsic rate of increase (rm) and also the net reproductive rate (R0) of C. septempunctata were 0.159 and 373.916, respectively. The mean generation time (T) of ladybird was 37.25 days and the population was doubled (DT) in 4.35 days. The population of C. septempunctata was able to multiply 3.45 times per week (rw). In order to determine rm and R0 of the melon aphid, twenty wingless adults were put separately into a leaf cage (10 × 60 mm) on cucumber leaves. The R0 and rm values of the aphid were 49.256 and 0.471, respectively. The T was 8.27 days and the population of the aphid was doubled within 1.47 days. Female aphids were able to multiply 27.03 times per week. Adult longevity was 13.8 ± 1.09 days and mean number of offspring produced per female was 49.05 ± 2.32 and mean number of females per female per day (mx) was 3.22 ± 0.59.