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Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

Destination Belmopan, Belize – Look who’s looking at you: Owl butterflies, Caligo sp.

 

A scary eye spot adorns the wing of an owl butterfly. Can it fool hungry predators?

 

This pair of owl butterflies might make a hungry predator turn back and run.

With Old Man Winter still holding his grasp on much of the nation, it is time to journey once again to tropical rainforests where we recently visited butterflies in cloud forests and along river banks, caterpillars hiding from predators, fierce bullet ants and less fierce green ants in trees, fungus beetles, walking sticks, and giant chinchemolles on the slope of a volcano. While photographing some stingless bees near a Mayan ruin near Belmopan, Belize, I glanced towards a nearby tree and was surprised to see the tree looking back at me. A closer inspection revealed a gorgeous owl butterfly.

Dead leaf or reptile head? 

These beauties have evolved a clever strategy for dealing with would-be predators. Intricate patterns of scales on the underside of their hindwings create an illusion of a large staring vertebrate eye, complete with pupal and iris. It is thought that this large eyespot is used by the butterfly to startle or otherwise confuse hungry predators such as birds or lizards. Studies have shown that the more closely the pattern resembles an eye the more likely a predator is to be deterred by the ruse. Another hypothesis suggests that the false eyespot may draw the attack of a predator away from a vital body part such as head or abdomen, to a less vital area such as the end of a wing, in much the same way the false head on the wings of the gossamer-wing butterfly we met a few weeks ago fools predators into a misdirected attack. Only the butterfly and its predators know for certain how well this deception works.

Orlando wrangles a handful of gorgeous owl caterpillars.

Caterpillars of the owl butterfly are similarly impressive creatures. By some strange good fortune I stumbled upon a butterfly house at a jungle resort and visited a large collection of owl butterfly larvae. These remarkable creatures have conspicuous forked tails and resemble tiny snakes, or perhaps large slugs. In their native habitat they consume leaves of heliconia, banana, and some palms. The pupal case or chrysalis of the owl butterfly is brown and dappled with two small golden spots on the sides near the head. A small horn adorns the top. While some books report the chrysalis to resemble a dead leaf, a Belizean caterpillar wrangler, Orlando, assured me that the chrysalis was a dead wringer for a local hognosed snake. This surely would give a hungry bird or lizard reason to pause before attacking these remarkable creatures. 

 

 

Like many of their kin, owl butterflies regularly feed on rotting fruit.

References

Bug of the Week thanks Orlando for teaching us the ways of the owl butterfly caterpillar and its chrysalis. James Castner’s “Amazon Insects” and the wonderful book “Insect Defenses” by David Evans and Justin Schmidt were used as references for this episode.