Population Parameters and Growth of Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) under Fluctuating Temperature

SIMPLE SUMMARY: The bean bug, Riptortus pedestris, is a polyphagous species that is an important pest of soybean fields in Asian countries. In this study, we examined the effects of constant and fluctuating temperatures on the development and reproduction of R. pedestris. The effects of thermal conditions were assessed by constructing age-stage, two-sex life tables from a constant temperature of 24 °C and simulated fluctuating temperatures of 24 ± 4 °C, 24 ± 6 °C, and 24 ± 8 °C. At a constant temperature, a number of R. pedestris life table parameters differed from those under fluctuating temperatures. Although similar pre-adult development periods were recorded under constant and fluctuating temperatures, the periods of female longevity and oviposition periods under fluctuating temperatures were significantly longer than those at a constant temperature. Given that temperature is an important abiotic factor for forecasting the population dynamics of arthropods in nature, determining the effects of fluctuating temperatures will make a valuable contribution to predicting R. pedestris population growth. ABSTRACT: In this study, we determined the influence of fluctuating temperatures on the development and fecundity of the bean bug Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) by collecting life table data for individuals exposed at a constant temperature (24 °C) and three fluctuating temperatures (24 ± 4 °C, 24 ± 6 °C, and 24 ± 8 °C). The raw life history data were analyzed using an age-stage, two-sex life table to take into account the viable development rate among individuals. Based on these analyses, the population projections enabled us to determine the stage structure and variability of population growth under different temperature treatments. Our results revealed shorter periods of immature development and a higher pre-adult survival rate at 24 ± 6 °C than under the other assessed temperature conditions. Furthermore, significant reductions in female longevity were recorded at 24 °C, whereas the fecundity, net reproductive rate, and intrinsic and finite rates of increase were highest at 24 ± 6 °C. These findings reveal that fluctuating temperatures have a positive influence on the life history traits of R. pedestris and indicate that observations made under constant temperatures may not explain sufficiently enough the temperature dependent biological performances of pests in the field.