It's the larva of a cecropia moth (Hyalophora cecropia) -- one of the members of a subfamily known as giant silkworm moths (Saturniinae). Like their Asian cousins (in a related family), the caterpillars in this family all spin cocoons out of lots of silk. But no one has made a successful commercial venture out of raising them.
Below are the five giant silkworm moths you're likely to see in the Washington, DC area. Aren't they beautiful?
Luna Moth
Actias luna
Typical wingspan: 4.5 inches
Larvae eat the leaves of a variety of native trees including birch, black gum, hickory, persimmon, sweet gum, and walnut.
Luna is the Roman moon goddess. These pale green moths do almost seem to glow at twilight.
(More pictures of the life cycle here)
Polyphemus moth
Antheraea polyphemus
Typical wingspan: 6 inches
Larvae eat the leaves of many shrubs and trees -- especially birch, rose, and willow, but many others.
In Greek mythology, Polyphemus was a cyclops -- a fitting namesake for a moth with big eyespots.
(More pictures of the life cycle here)
Promethea moth
Callosamia promethea
Typical wingspan: 3-4 inches
Larvae eat the leaves of native shrubs and trees including spicebush, sassafras, cherry, tulip tree, ash, and many others.
In Greek mythology, remember, Prometheus was the one who gave fire to humans and was sentenced to eternal punishment for it.
(More pictures of life cycle here)
Photo credit: Circeson
Tuliptree silkmoth
Callosamia angulifera
Typical wingspan: 3-4.5 inches
Larvae eat the leaves of the tulip tree, which is common in our local forest -- but the branches are usually out of reach. Still, our caterpillar book recommends looking up at dusk to see them flying.
Photo credit: Linda Tanner
Cecropia moth
Hyalophora cecropia
Typical wingspan: up to 6 inches
Larvae eat the leaves of many woody plants including maple, birch, apple, cherry, and others -- apparently including blueberry.
In Greek mythology, Cecrops was a half-man, half-snake born from the earth. He was the first king of Athens, and first to worship Zeus.
(More pictures of life cycle here)
Much of this info on host plants comes from a great field guide called Caterpillars of Eastern North America: A Guide to Identification and Natural History
-- check it out!