Comparison of the biology of Frankliniella intonsa and Megalurothrips usitatus on cowpea pods under natural regimes through an age-stage, two-sex life table approach

Two thrips, Megalurothrips usitatus (Bagnall) and Frankliniella intonsa (Trybom) are major pests of cowpea in South China. To realistically compare the growth, development and reproductive characteristics of these two thrips species, we compared their age-stage, two-sex life tables on cowpea pods under summer and winter natural environmental regimes. The results showed that the total preadult period of M. usitatus was 8.09 days, which was significantly longer than that of F. intonsa (7.06 days), while the adult female longevity of M. usitatus (21.14 days) was significantly shorter than that of F. intonsa (25.77 days). Significant differences were showed in male adult longevity (10.68 days for F. intonsa and 16.95 days for M. usitatus) and the female ratio of offspring (0.67 for F. intonsa and 0.51 for M. usitatus), and the total preadult period of M. usitatus (16.20 days) was significantly longer than that of F. intonsa (13.66 days) in the winter regime. The net reproductive rate (summer: R₀ = 85.62, winter: R₀ = 105.22), intrinsic rate of increase (summer: r = 0.3020 day^-1, winter: r = 0.2115 day^-1), finite rate of increase (summer: λ = 1.3526 day^-1, winter: λ = 1.2356 day^-1) and gross reproduction rate (summer: GRR = 139.34, winter: GRR = 159.88) of F. intonsa were higher than those of M. usitatus (summer: R₀ = 82.91, r = 0.2741, λ = 1.3155, GRR = 135.71; winter: R₀ = 80.62, r = 0.1672, λ = 1.1820, GRR = 131.26), and the mean generation times (summer: T = 14.73 days, winter: T = 22.01 days) of F. intonsa were significantly shorter than those of M. usitatus (summer: T = 16.11 days, winter: T = 26.25 days). These results may contribute to a better understanding of the bioecology of different thrips species, especially the interspecific competition between two economically important cowpea thrips with the same ecological niche in a changing environment.