Introduction to Electronic Monitoring of the Feeding Behavior of Phytophagous True Bugs

Electrical penetration graph technique, or electropenetrography (EPG), is a method of indirectly visualizing the feeding of piercing-sucking insects within plant tissue, permitting quantification of feeding behaviors such as stylet penetration, salivation, and ingestion from specific plant tissues. In this chapter, the basic principles of EPG are explained, and a brief history of development of the technique is presented, from early alternating current (AC) monitors, to direct current (DC) monitors, and finally to a combined AC-DC monitor that offers a choice of applied current and amplifier sensitivities. The signals, called waveforms, generated by EPG recordings are explained and related to the internal ingestion sites (e.g., xylem vessels, stem parenchyma). The two components of the waveforms, resistance to electron flow (R) and biological voltages (emf, or electromotive force), are distinguished. Biological information is reviewed for the five families of phytophagous Heteroptera that have been studied to date using EPG: Miridae (Cimicomorpha) and Blissidae, Coreidae, Pentatomidae, and Plataspidae (Pentatomomorpha). Examples are provided of the role of EPG in characterizing damage from feeding by species of Pentatomidae, the most extensively studied family.