During research on the life history characteristics of insidious flower bug, Orius insidiosus (Say), fed soybean aphids, Aphis glycines Matsumura, the mouthparts of some predators were covered by a substance excreted from the cornicles of attacked aphids. The cornicle exudate was found to encumber both nymphs and adults of O. insidiosus causing death because of molting failure and starvation. Among predator stages, first instars were most severely affected. Feeding frequency affected the number of predators affected by the exudate, with predators fed more often having higher rates of exudate exposure and mortality. Soybean aphids produce exudate during all life stages, and its production does not seem to compromise the survival of the aphid. The exudate also seems to contain an alarm pheromone as evidenced by increased movement and activity of aphids in the vicinity of exudate-producing aphids. The potential impact of the aphid’s cornicle defenses on aphid–predator dynamics in soybean, Glycine max (L.) Merr., is discussed.