Eyespots of the spicebush swallowtail butterfly caterpillar protect it from predators because their tear shape creates an illusion of movable, watchful eyes.

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"The directionality of P. troilus's stare is achieved through a very simple design feature: the shape of the dark pupillary marking in the center of the eye. That marking, instead of being circular as it commonly is in actual eyes, is tear-shaped in the caterpillar's imitative version. It consists essentially of two portions: the basic circular marking, and a triangular anterior add-on that merges seamlessly with it. Leave out the add-on, and you have an eye with a circular pupil that is not nearly as able to convey the impression of looking forward or to the side." (Eisner 2003:96-97)

For Love of InsectsThe Belknap Press of Harvard University PressOctober 31, 2005
Thomas Eisner

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Coastal Spicebush SwallowtailPapilio troilusSpecies

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