Moths, Pacific Northwest
Eyed Owl Moth is fairly common in the Pacific Northwest. The eyed owl moth is one of our biggest moths, having up to a 14 cm wingspan. It has brownish wings with a black and white, wavy line on each. It has a small, mostly yellow eyespot on each fore wing and larger blue, black, and yellow eyespots on the hind wings. Underneath, the moths’ wings look like dead leaves.
Eyed owl moths are usually found in forests, but can also be seen in marshes and parks. These moths leave their cocoons in the afternoon in early May. Neither the male or female adult moths eat; in fact, they don’t even have mouth parts!
As soon as she has fully emerged and rested (later that night), the female begins releasing pheromones. Male moths can detect the scent from miles away and come to mate with her.
After mating, the female will lay up to 5 eggs on the underside of a leaf. When caterpillars hatch from their eggs, they first eat their own eggshells, then start working on leaves. Eggs are always laid on the right kinds of leaves, so caterpillars don’t have to look for food. Eyed owl moth caterpillars are bright green with yellow stripes and red and silver spots. They grow up to 8 cm long
Host plants of the caterpillars include many trees and shrubs, such as oaks, maples, pines, hawthorns, mountain ash, bitter cherry, elderberry, alders, sassafras, blueberries, and willows. As they grow, caterpillars molt. They molt four times before they are fully grown.
When the caterpillar is ready, it wraps itself in a leaf and builds a cocoon with silk from its mouth.
The cocoon hardens and turns brown. Inside the cocoon, the caterpillar will turn into a pupa (resting stage). If it is early summer, the pupa will change into an adult moth and mate. If it is late summer or early fall, the pupa will overwinter and emerge the following May.
Some cocoons stay stuck to a tree branch all winter. Others fall to the ground when the leaves fall.
You can tell a male adult moth from a female by its antennae. The male has large, feathery antennae which help it detect the female’s pheromones.
Eyed owl moths use mimicry to defend themselves. Besides looking like dead leaves or bark when their wings are folded, these moths will open their wings suddenly, revealing the large eyespots. These eyespots mimic an owl’s eyes and can startle a predator.
These moths are nocturnal, only flying at night. By day, they use their camouflage to hide from predators. Predators of adults include small mammals, such as mice, squirrels, and bats, as well as birds. Caterpillars also do most of their feeding at night.