Previous evaluation of two specialist predators, Laricobius nigrinus (Coleoptera: Derodontidae) and Sasajiscymnus (Pseudoscymnus) tsugae (Coleoptera: Coccinellidae), and a generalist predator, Harmonia axyridis (Coleoptera: Coccinellidae), of A. tsugae, demonstrated that intraspecific competition occurred in these species, and negatively affected feeding by H. axyridis, and egg production by all species. The nature of this interference was examined in the laboratory using choice tests. Previously mated female predators were placed separately into Petri dish bioassays containing eastern hemlock branch clippings infested with A. tsugae. To examine intraspecific effects on feeding, H. axyridis was allowed to choose between branches recently contacted by conspecifics and untreated controls. Intraspecific effects on egg production were assessed for all species similarly. Additional treatments containing recently deposited conspecific eggs were tested also. Predator choice of feeding site, consumption of conspecific eggs, oviposition location, and egg production were documented in each trial. For H. axyridis, significantly less feeding and egg production occurred on each set of treatment branches, and conspecific eggs were consistently cannibalized. For L. nigrinus and S. tsugae, conspecific contact with branch clippings did not significantly affect egg production; however, the addition of conspecific eggs significantly reduced oviposition at those locations. Egg cannibalism was rare in the specialist species. These studies indicate that intraspecific interference on feeding by H. axyridis, and egg production in all species, may result from indirect competition in response to physical or chemical cues. Reproductive interference by H. axyridis may also result from direct competition, in the form of egg cannibalism.