Three bacterial isolates, aFlavobacteriumsp.,Erwinia herbicola, andXanthomonas campestris, stimulated seedcorn maggot,Delia platura(Meigen), oviposition when tested either alone or in combination. Twenty bacteria with varying abilities to inhibit growth of these stimulatory bacteria were isolated from soil. These antagonistic bacteria either stimulatedD. platuraoviposition themselves or did not reduce inocula of the other organisms enough to reduce egg laying. In observation experiments, flies stayed longer and laid more eggs on inoculated substrates, even when they could not actually contact the bacterial inoculum during oviposition.