Effect of Fluctuating Temperatures on Development of Immature Russian Wheat Aphid (Homoptera: Aphididae) and Demographic Statistics

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Abstract
The effect of temperature on developmental rates and demographic statistics of apterous and alate Russian wheat aphids (RWA), Diuraphis noxia (Mordvilko), was studied in the laboratory using three fluctuating temperature regimes that were similar to average and extreme low and high temperature conditions of late spring in eastern South Dakota. An estimate of the lower threshold for development of immatures was determined (4.1°C). Degree-day (DD) requirements from birth to the onset of reproduction were determined for apterae (139 DD) and alatae (158 DD). Gross and net reproductive rates of both morphs were greatest at the low temperature regime and declined with increasing temperature. When expressed on a time scale of days, intrinsic rates of increase of both morphs were highest and mean generation time shortest at the high temperature regime. On a time scale of DDs, mean generation times converged but intrinsic rates of increase did not; intrinsic rates of increase of both morphs were highest for the low temperature regime and decreased with increasing temperature. For each temperature regime, the intrinsic rate of increase of apterae exceeded that of alatae.