Numerous species of epigeal arthropods collected from apple orchards in southern Ontario were predaceous on larvae and pupae of the apple maggot,Rhagoletis pomonella(Walsh). However, few species fed extensively on dipterous prey and the numbers of individuals that were serologically positive with antiserum toR. pomonellawere generally low. The ground beetlesAmara aeneaDeGeer,Harpalus aeneusF., andPterostichus melanariusIlliger; the staphylinids,Philonthusspp.; the ants,Formica fuscaL. andMyrmicasp.; and the spider,Trochosa terricolaThorell, appeared to be the most frequent predators ofR. pomonella.