Bad Hair Day

What am I looking at?

This is the face of a caterpillar of the peacock moth (Automeris io), also called the Io moth. It has a thick covering of venomous spines (1) all over its body except its head. You can also see its segmented true legs (2); its prolegs, which end in a semicircle of hooks called crochets (3); its black simple eyes, or ocelli – six per side (4); and its chewing mouthparts (5), which are powered by muscles that fill most of its head. Click on the right arrow to see what the adult moth looks like.

Biology in the background

These moths live in North America. Their caterpillars feed on a wide variety of trees and plants. The species has two common names, both based on the appearance of the adult moth. Its first common name refers to the large eyespots on its wings because they resemble the spots on a peacock’s feathers. Its second common name took its inspiration from Greek mythology; Io (pronounced EYE-oh) was a famed beauty – the mortal lover of Zeus, king of the gods, and the mother of the mythological hero Hercules. However, unlike Io, who was cursed with immortality by Zeus’s wife, the adult moths of this species live only one to two weeks.  

As you can see in the main image, these caterpillars are covered with a dense thicket of spines; the spines contain venom that can cause painful stings, like those of nettles, upon only a very light touch. The composition of the venom hasn’t been well studied, but it might contain formic acid and/or histamine.

The caterpillar’s eye-like markings, called eyespots, are a common element of antipredator deception tactics among many animal species. Insects like praying mantises, katydids, walking sticks, moths, and butterflies use such tactics to either startle oppressors with a sudden reveal of large “eyes” or to redirect an attack to a nonvital part of their body. The adult moths of the species are sexually dimorphic – meaning the appearance and anatomy of males and females are different; in the case of peacock moths, the females are slightly larger and brown, and the males are smaller and yellow.

A peacock moth caterpillar can grow up to 7 centimeters long, or roughly the size of a human pinky finger. An adult can have a wingspan of up to 9 centimeters, or roughly the size of a human ring finger.  

Technique

These images were created using macrophotography.