Developmental Response of Three Geographic Isolates ofLysiphlebus testaceipes(Hymenoptera: Aphididae) to Temperature

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Abstract
Using greenbugs, Schizaphis graminum (Rondani), as a host, the number of days required for development, survival, and sex ratio (female:male) were studied at five constant temperatures (10, 14, 18, 22, and 26°C) for colonies of Lysiphlebus testaceipes (Cresson) collected in south Texas, central Oklahoma, and central Nebraska. Developmental rate and lower development threshold were described by a linear function and compared among wasp colonies. The temperature thresholds for development from egg to adult for the Nebraska, Oklahoma, and Texas wasp colonies were estimated to be 5.64, 6.61, and 6.42°C, respectively; corresponding degree-day requirements for development were 181.2, 169.5, and 188.0 DD, respectively. No differences in developmental rate or lower development threshold estimates were observed among the wasp colonies. However, adult survival at 10°C was greater in the Nebraska colony, suggesting that there may be variation in the ability of L. testaceipes populations to tolerate and survive cold temperatures.