Abstract
Opius melleus Gah. and O. lectus Gah. were the only parasites of Rhagoletis pomonella (Walsh) found in southern Ontario during a 4-year survey. The parasites were found only in the Niagara Region on the slope of the Niagara Escarpment and between it and Lake Ontario. The population of parasites was low though they appeared to be well adapted to attack R. pomonella. They were found in, or adjoining, unsprayed sites where there was shrubby growth under the trees infested by R. pomonella.