Thermoregulation by Diabrotica undecimpunctata howardi and potential effects on overwintering biology
1987
Meinke, Lance J. | Gould, Fred
In North Carolina, southern corn rootworm (SCR), Diabrotica undecimpunctata howardi Barber, adults of both sexes (diapausing and nondiapausing) elevate body temperature (Tb) above ambient air temperature (Ta) by basking in direct sunlight on clear fall and winter days when Ta < 13 °C (Tb-Ta range: 0.8-13.3 °C). On cloudy days, SCR adults did not exhibit basking behavior and Tb was more highly correlated with Ta, ground temperature (Tg), and substrate temperature (Ts) than on clear days. Ts was the best predictor of Tb regardless of Ta and the presence or absence of adult basking behavior (fall basking SCR, Ts vs. Tb: R² = 0.94, Ta vs. Tb: R² = 0.41; fall nonbasking SCR, Ts vs. Tb: R² = 0.85, Ta vs. Tb: R² = 0.55). These results suggest that SCR thermoregulation at low Ta is ectothermic regulation by microhabitat selection. Elevation of Tb by thermoregulation was often of sufficient magnitude to affect SCR behavior (flight, feeding, mating) and preovipositional development rate. This could explain why gravid SCR females have been found in North Carolina by 6 January when Ta's were too low for development. The relationship of Tb to Ta on cold sunny days would be important to include in any predictive day-degree model of SCR postdiapause development or SCR endoparasite development in the field.
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