This video was prepared for Grit Kunert and Alexander Schwarzkopf of the Max Planck Institute for Chemical Ecology. It demonstrates aphid feeding behavior, specifically how an aphid samples leaf cells by inserting its stylet into a cell and injecting saliva to chemically sense whether the plant is a host. The pea aphid is a specialist on legumes. The saliva injection also aids the aphid in finding the phloem, the nutritive source for the aphid. This process can be monitored by the Electrical Penetration Graph (EPG) technique, in which voltage changes are generated depending on the location of the stylet in the leaf.