The green belly stink bug, Dichelops melacanthus (Dallas), has become an important pest of maize in the Neotropics in recent years. Thus, more studies are needed to understand its feeding behavior in order to find ways to reduce its damage. One way to do so is through the technique known as electrical penetration graph (EPG), which allows unveiling the stylet activities of piercing–sucking hemipterans. The goal of this study was to investigate the feeding behavior of D. melacanthus on maize seedling and create a waveform library. The feeding activities were monitored on maize stem using the new AC–DC EPG monitor. Seven distinct waveforms were recorded: Z, Np, O, Dm1, Dm2, Dm3a, and Dm3b, grouped into two families—P (Em1) and I (Dm1, Dm2, and Dm3). Histological studies of severed stylets were carried out during Dm1, Dm2, and Dm3a waveforms to correlate with the specific activities. Z, Np, and O represented the nonprobing phase; in Z the insect was still on the stem surface; in Np the insect was walking on the stem; and in O occurred egg deposition. Dm1, Dm2, and Dm3 correspond to the probing waveforms, where Dm1 represents the insertion and deep pathway of the stylets in plant tissue and secretion of salivary sheath; Dm2 represents the sap ingestion from xylem vessels; and Dm3 represents the cell rupturing feeding (waveform Dm3a), and the ingestion of cellular contents derived from mechanical (laceration) and chemical (maceration) degradation (waveform Dm3b).