Electronically monitored feeding behavior, reproduction, and honeydew production of greenbug,Schizaphis graminum(Rondani), biotypes C (GBC) and E (GBE) were studied on three genotypes of wheat,Triticum aestivumL. We studied resistant and susceptible plants to determine how host-plant genotype alters greenbug feeding behavior and honeydew production on wheat and the relationship between feeding behavior and greenbug resistance. Greenbugs monitored for 24 h on resistant plants performed recognized behaviors (stylets withdrawn from plant, probing, salivating, and ingesting from phloem) 2- to 3-fold more frequently than on susceptible plants. Average duration of a given behavioral event was not modified by resistance, except in the case of phloem ingestion. Total time over 24 h spent with stylets withdrawn from the plant was increased on resistant plants, as was total salivation time, whereas total time spent ingesting from phloem was reduced. Greenbugs on susceptible plants achieved phloem ingestion longer than 15 min within 30 min of the first phloem contact, but those on resistant plants failed to achieve this for up to 4 h. Honeydew production over 5 d was unaffected by host plant. Resistant plants induced greenbugs to expel more honeydew per unit dry-matter weight gain. The data suggest that the greenbug's ability to damage its host plant may allow it to more quickly accept nutritionally enriched phloem sap associated with feeding damage and may result in production of larger, more fecund greenbugs.