Developmental response of three geographic isolates of Lysiphlebus testaceipes (Hymenoptera : Aphididae) to temperature

Using greenbugs, Schizaphis graminum (Rondani), as a host, the number of da ys required for development, survival, and sex ratio (female:male) were stu died at five constant temperatures (10, 14, 18, 22, and 26 degreesC) for co lonies of Lysiphlebus testaceipes (Cresson) collected in south Texas, centr al Oklahoma, and central Nebraska. Developmental rate and lower development threshold were described by a linear function and compared among wasp colo nies. 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 degreesC, 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 observe d among the wasp colonies. However, adult survival at 10 degreesC was great er in the Nebraska colony, suggesting that there may be variation in the ab ility of L. testaceipes populations to tolerate and survive cold temperatur es.