Ramirez, C.C. Centro de Investigación en Biotecnología Silvoagrícola, Instituto de Biología Vegetal y Biotecnología, Universidad de Talca, Casilla 747, Talca, ChileThe effects of parasitisation by Aphidius ervi on the feeding behaviour of the aphid Acyrthosiphon pisum were studied. There was progressive increase in the time devoted to xylem ingestion (G waveform) and concomitant decrease in time devoted to phloem ingestion (E2 waveform) in parasitized relative to unparasitized aphids, as the time from parasitisation increased. These changes are interpreted as a way aphids compensate for metabolic changes occurring during parasitisation.