Supercooling points of Lysiphlebus testaceipes and its host Schizaphis graminum.

Supercooling points (SCPs) were measured for various life stages of male and female Lysiphlebus testaceipes (Cresson) parasitoids, along with mummies and its aphid host, Schizaphis graminum (Rondani). Some parasitoids were acclimated (4 h at 10 degrees C before cooling down to the SCP) to determine whether this could significantly lower the SCP. Acclimation did not improve SCPs for L. testaceipes. An inverse relationship between age of the adult parasitoid and its SCP was detected. Nonacclimated male and female parasitoids older than 12 h after emergence spontaneously froze at the warmest mean temperatures (-20.32 +/- 1.32 and -22.55 +/- 0.62 degrees C [SE], respectively). Younger female adult parasitoids (<6 h after emergence) and mummies had mean SCPs less than -26 degrees C. The SCP for the greenbug host was slightly warmer at -25.98 +/- 0.10 degrees C. Knowledge of SCPs for L. testaceipes and its host S. graminum help provide insights about their ability to successfully function throughout the winter in the southern Great Plains.