EPG Procedures for True Bugs (Heteroptera)

Abstract

Since its development, the electrical penetration graph (EPG) has been used to record the feeding behavior of mostly small, relatively weak insects (aphids and leafhoppers). Recently the larger, more robust true bugs (e.g., pentatomids) began to be monitored via EPG, and some problems were encountered, especially related to gold wire attachment. Wiring procedures involve the choice of an electrically conductive adhesive (silver paint or silver glue) and methods to immobilize the bugs to facilitate the process and guarantee successful wiring by sanding the cuticle. Histological studies are often coupled with EPG recordings to correlate waveforms with the location of the salivary sheaths or stylets in the plant tissue. EPG can also be applied in quantitative studies to determine counts and durations of the waveforms recorded and then to compare via statistical analysis. At the start of EPG research, essential variables must be standardized, such as the ideal starvation period (if required), recording times, and laboratory environmental conditions. Appropriate experimental design and the acceptable sample size (number of insects recorded per treatment) are also important considerations.