Thermal activity thresholds of the parasitic wasp Lysiphlebus testaceipes and its aphid prey: implications for the efficacy of biological control

Adult parasitoids Lysiphlebus testaceipes Cresson (Hymenoptera: Aphidiidae) lose locomotory function and enter chill coma at significantly lower temperatures (-0.1 and -8.0 degrees C, respectively) than their second-instar hosts, the black bean aphid Aphis fabae Scop. (Hemiptera: Aphididae) (5.6 and 2.3 degrees C, respectively). Parasitoids are also more heat tolerant, stop walking at 41.4 degrees C, with heat coma at 44.1 degrees C, than the aphid (39.1 and 43.0 degrees C, respectively). Furthermore, across a range of temperatures (0-20 degrees C), L. testaceipes has considerably faster walking speeds than A. fabae. These data are discussed in relation to the climatic conditions under which L. testaceipes would be an effective control agent, and the likelihood of establishment and spread in northern European climates.