Effects of Constant and Fluctuating Temperatures on Developmental Rates and Demographic Statistics of the English Grain Aphid (Homoptera: Aphididae)

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Abstract
Relationships between temperature and developmental rate of immature apterous and alate English grain aphids, Macrosiphum avenae (F.), were studied in the laboratory using constant and fluctuating temperatures. Estimates of lower (4.0°C) and upper (24.6°C) developmental thresholds were determined using constant temperatures. Developmental rates and age-specific life table statistics were determined using fluctuating temperature regimes that simulated average and extreme low and high temperature conditions occurring during late spring in South Dakota. Developmental rates of cohorts exposed to low and average fluctuating temperatures were consistent with expected developmental rates based on a degree-day model incorporating lower and upper thresholds obtained from constant temperature studies. Developmental rate appeared to slow in M. avenae exposed to high fluctuating temperatures. Life table statistics expressed on a degree-day time scale differed among apterous and alate M. avenae exposed to identical temperature regimes. At each temperature regime, population growth rates of apterae exceeded those of alatae. On a degree-day time scale, population growth rates of both morphs were greatest at low temperatures and declined as temperature increased.

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