How to identify a cecropia moth
Cecropia is hard to mistake once you see the scale. Wingspans reach 5 to 7 inches, making it the biggest moth native to North America. The wings are deep grayish-brown, crossed by reddish bands edged in white, and each wing bears a kidney- or crescent-shaped white spot with a red center. The body is stout and furry with a red collar behind the head and a red-and-white banded abdomen. The feathery antennae, broadest on males, help males detect a female's scent from a long distance.
Where the cecropia moth lives
Cecropia moths are found across the eastern and central parts of the continent, from southern Canada down into the Southeast and west to the Great Plains. In open records they show up most in New York, Vermont, New Hampshire, Texas, and Massachusetts. They live in deciduous woodlands, forest edges, orchards, and leafy suburbs where their host trees are common.
When cecropia moths fly
Unlike the multi-brooded luna, the cecropia has just one generation a year. Adults emerge and fly in late spring, peaking in May and June. The flight window is short, so a warm, calm night in those two months is your main chance. Males often take to the air late at night, homing in on the pheromone of a freshly emerged female.
Caterpillars, host plants, and life cycle
The caterpillar does every bit of the eating. Mature cecropia caterpillars are spectacular: up to four inches long, bright bluish-green, and studded with rows of blue, yellow, and orange knob-like tubercles. They feed on a wide range of woody plants including maple, cherry and other wild plums, birch, apple, and lilac. In fall the caterpillar spins a large, tough, spindle-shaped silk cocoon attached lengthwise to a twig, where it overwinters as a pupa. The adult emerges the next spring with no working mouthparts, so it cannot feed and survives only a week or two, just long enough to mate and lay eggs.
How to see a cecropia moth at night
Cecropia moths come to artificial light, with ultraviolet far more effective than white LED. The current best explanation is that bright light disrupts a moth's flight orientation: moths keep a natural light source like the moon at a fixed angle, and a close bulb throws off that internal compass. To look for one, run a UV or mercury-vapor lamp against a white sheet on a warm, still night in May or June, ideally near mature hardwoods. Because the adult flight is so brief, new birders also have luck finding the big overwintering cocoons on bare twigs in winter. If you are new to this, start with mothing for beginners, and compare your find with the luna moth and polyphemus moth, its giant silk moth cousins.