Comparative Study of Life Table Parameters of Hippodamia variegata (Col.: Coccinellidae) vs. Aphis fabae (Hem.: Aphididae)

To provide reliable information concerning reproductive potential of Hippodamia variegata Goeze and its prey (Aphis fabae), their related life tables were studied under controlled laboratory conditions (at 23ºC). The unprocessed data of life tables were analyzed taking the Euler-Lotka as the basis model. Standard error of population growth parameters was calculated using the Jackknife re-sampling method. The Mann-Whitney U test was utilized to determine differences in population parameters of H. variegata and of A. fabae. The intrinsic rate of increase (rm) of ladybird was 0.197±0.002d-1. Other table parameters, including net reproductive rate (R0), mean generation time (T), the finite rate of increase (λ) and the Doubling Time (DT) were estimated as 365.43±22.09 offsprings, 29.96±0.37 d, 1.218±0.002 d-1 and 3.52±0.033 d, respectively. These parameters were estimated for A. fabae as: rm= 0.309.±0.01 d-1, R0= 41.98±4.6 offspring, T = 12.1±0.21 d, λ= 1.36±0.015 d-1 and DT=2.24±0.078 d. A comparison of the two life table parameters showed that there existed significant differences between life table parameters of H. variegata and those of A. fabae. In all cases, the aphid exhibited a more prominent reproductive trait.