The human visual system may retain ancestral mechanisms uniquely dedicated to the rapid detection of immediate and specific threats (e.g. spiders and snakes) that persistently recurred throughout evolutionary time. We hypothesized that one such ancestral hazard, spiders, should be inherently prioritized for visual attention and awareness irrespective of their visual or personal salience. This hypothesis was tested using the inattentional blindness paradigm in which an unexpected and peripheral stimulus is presented coincidentally with a central task-relevant display. Despite their highly marginalized presentation, iconic spiders were nonetheless detected, localized, and identified by a very large proportion of observers. Observers were considerably less likely to perceive 1) different configurations of the same visual features which diverged from a spider prototype, or “template”, 2) a modern threatening stimulus (hypodermic needle) comparable in emotional salience, or 3) a different fear-irrelevant animal (housefly). Spiders may be one of a very few evolutionarily-persistent threats that are inherently specified for visual detection and uniquely “prepared” to capture attention and awareness irrespective of any foreknowledge, personal importance, or task-relevance.