Neonate and inexperienced Sceloporus malachiticus (Squamata: Iguanidae) have an unlearned response to the aposematic color pattern of the milkweed bug Oncopeltus fasciatus. This response may be interpreted as either an avoidance of the aposematic color pattern or a preference for the uniformly colored alternate prey. The young lizards avoid other characteristics of the aposematic insect, but this avoidance decreases with age or experience. These results collectively suggest an evolutionary interaction between the behavior of the predator and the appearance of its potential prey.