Eye Spots Deter Animals

close up photograph of green caterpillar on a leaf during the day

Biological Strategy

Coastal spicebush swallowtail

AskNature Team

Image: Katja Schulz / Flickr / Some rights reserved

Protect From Animals

Animals–organisms that range from microscopic to larger than a bus–embody a wide variety of harms to living systems, including other animals. They threaten through predation, herbivory, defense, and parasitism, and they compete for resources such as water, nutrients, and space. Any given living organism commonly faces threats from a variety of animals, requiring strategies that effectively defend from each. Trout and other bony fish, for example, escape predators by having scales made of very thin, flake-like pieces of bone covered with slippery mucus. They also have behavioral strategies such as camouflage, fast swimming, and twisting and turning to achieve release from a predator’s grip.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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

“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)