Animals can reduce the risk of being preyed upon by foraging less in the presence of predators. Animals often face a diverse group of predators that vary in their effectiveness at preying upon the animal, and thus pose different potential risks. In laboratory microcosms, we investigated the ability of the spotted cucumber beetle, Diabrotica undecimpunctata howardi (Barber), a polyphagous herbivore, to accurately recognize dangerous predators versus taxonomically related predators that posed no true risk, and to adjust the intensity of their antipredator behavior accordingly. Spotted cucumber beetles reduced their feeding, and reduced damage to host plants, in the presence of the large wolf spider Hogna helluo (Hentz), which previous experiments identified as the most dangerous predator we examined. Beetles did not significantly alter their feeding rate in the presence of 3 other less-dangerous predators. Laboratory mesocosm studies verified that, indeed, Hogna was the most effective at capturing D. u. howardi in a structurally complex environment more similar to that in the field. Spotted cucumber beetles responded to Hogna, whereas several similar-sized but less-dangerous predators were ignored, suggesting that D. u. howardi may have been able to recognize Hogna specifically. Our results suggest that reduced feeding by herbivores as a strategy to reduce predation risk can allow predators to improve biological control even when actual predation does not occur.