Anyone seeing a huge flying insect at the bottom of a bush or plant would attract their attention immediately. Particularly, if the large-appearing butterfly is actually a large moth with a hairy body that resembles a tarantula. This moth can achieve the wingspan of 5.5 inches.
The Polyphemus moth is unlikely to be confused with any other moth in the Pacific Northwest because of its size, tan color and translucent eyespots. This member of the Giant Silk Moth family is both large and furry. The antennae are also feathery. Eyespots on the wing are oval-shaped and have rings of yellow, black and blue in them. If startled, they will open and close their wings, flashing their eyespots as a way to disorient a would-be predator.
They can be found in parks and deciduous forests in urban, and rural areas. Like most moths they are nocturnal and attracted to lights.
Caterpillars are multicolored. Their soft bodies are covered in thin black, yellow and white rings. As it matures, it turns all white, retaining tiny black dots while growing 4 bristly spikes near its head. They eat a variety of plants and pupate on whatever they are eating.
The most notable features of the moth are its large, purplish eyespots on its two hind wings. The eye spots give it its name — from the Greek myth of the Cyclops Polyphemus. The species is widespread in continental North America. The caterpillar can eat 86,000 times its weight in a little less than two months.
The life cycle of the moth is much like that of any other Saturmiidae species. It lays flat, light-brown eggs on the leaves of a number of host plants, including: birch, willow, oak, maple, hickory, pear, plum, peach, apricot, cherry and elm.
When the eggs hatch, small yellow caterpillars emerge. As the caterpillars age, they molt five times. Each instar is slightly different, but on their fifth and final instar, they become a bright green color with silver spots on the sides. They feed heavily on their host plant and can grow up to 3-4 inches long. They then spin cocoons of brown silk, usually wrapped in leaves of the host plant.
Two broods generally hatch each year, one in early spring and one in late summer. The moths enclose and then must pump their wings with fluid (hemolymph) to extend them. The females emit pheromones, which the male can detect through his large antenna. Males can fly for miles to reach a female. After the moths mate, the female spends the majority of the remainder of her life laying eggs, while the male may mate several more times. Adults of this family of moths have a vestigial mouth, meaning their mouth parts have been reduced. Because of this, they do not eat and only live as adults for less than one week.
The Polyphemus moth uses defense mechanisms to protect itself from predator. One of the most distinctive mechanisms is a distraction display that serves to confuse, or simply distract predators. This involves the large eyespots on its hind wings, which give the moth its name. Eyespots are also a startle or distraction pattern, used for camouflage, deception and blending coloration. Most startle patterns are brightly colored areas on the outer body of already camouflaged animals. The pattern on the hind wings of the Polyphemus moth resembles that on the head of the great horned owl.
Polyphemus moths spin oval-shaped cocoons and incorporate some leaves from plants. Once inside the cocoon, the caterpillar enters the pupa stage and changes into a moth. However, the pupa stays in a resting state for the winter until the temperatures warm in the spring. The moth’s brief appearance provides us with an opportunity to see one of our largest moths.
Enjoy summer and the beauty of Boundary County.