Current Issue

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

Here's looking at you - Owl butterflies, Caligo sp.


A scary spot adorns the wing of an owl butterfly.


With the northeast firmly embraced by winter’s chill, it’s time to move south to the tropical rainforests of Belize. While photographing some stingless bees, I glanced at a nearby tree and was surprised to see the tree staring back at me. A closer inspection of the tree revealed a large owl butterfly.

Orlando wrangles a handful of gorgeous owl caterpillars.

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 the head or abdomen to a less vital area such as the end of a wing. Only the butterfly and its predators know for certain how well this deception works.

Dead leaf or reptile head?

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 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. 

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


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 Penny Gullan and Paul Cranston’s “The Insects” were used as references for this episode.