Abstract
The life history and predation rate of Lemnia biplagiata (Swartz) fed on Aphis gossypii Glover was studied at 25C in the laboratory. The raw data were analyzed based on the age-stage, two-sex life table to take the variable developmental rate among individuals and both sexes into consideration. The intrinsic rate of increase (r) is 0.1570 d 1 , the Þnite rate of increase () is 1.170 d 1 , the net reproduction rate (R0) is 291.1 offspring per individual, the mean generation time (T) is 36.2 d, and the gross reproduction rate (GRR) is 604.8 offspring. L. biplagiata consumed 430 42 aphids (mean SD) during the larval stage. The mean consumption rate for an adult during the Þrst 25 d (aged 14 Ð38 d from birth) is 1,548 118 aphids. The mean consumption for an older adult (aged 60 Ð119 d from birth) is 1,319 1,259 aphids. When the survival rate is taken into account, the net consumption rate is 3,022 aphids per individual during the total life span. The transformation rate from prey population to predator offspring is 10.4. The relationship among GRR, R0, and the preadult survival rate (la) is proven as R0 la GRR GRR. However, when applying the female age-speciÞc life table to a two-sex population, due to the difÞculty in determining the preadult mortality of the females, the calculated age-speciÞc survival rate and fecundity are possibly incorrect and consequently the relationship among GRR, R0, and la also may be incorrect.
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