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Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

A season of silk moths continues with Cecropia moth, Hyalophora cecropia


Some say Cecropia is the most beautiful of all silk moths. Hard to argue with that. Photo credit: Karin Burghardt


This mating pair was discovered in April on a viburnum at a nursery in New Jersey. Photo credit: Gordon and Sheri Raupp

Greek mythology has it that Cecrops, ruler and king of the city of Cecropia, was born from the earth as half man, half snake, hence the literal translation of Cecropia is “face with a tail.” Legends surrounding Cecrops credit him with founding key elements of civilized life, including the institution of marriage. From what I have seen this spring, Cecropia is a name most befitting these largest members of the North American silk moth clan. This by virtue of the fact that they so often are found engaged in the act of mating, which I suppose might be construed as the insect equivalent of marriage.

While much recent attention has focused on dramatic declines in insect biodiversity around the world, by many accounts the spring of 2019 has been a notably good one for silk moths and butterflies in our region. With ample rainfall and luscious plant growth last year, perhaps silk moths produced a bumper crop of overwintering pupae that translated into fine crop of silk moths this season. In a previous episode, we met another silk moth, the gorgeous Luna, rescued from a sidewalk near a school. Over the past few weeks several folks have sent beautiful images of Cecropia and other silk moths, including Imperial Moth and Royal Walnut Moth we met in previous episodes. As mentioned above, Cecropia spends the winter as a pupa nestled within a silken cocoon sometimes cloaked with bits of dead leaves. Cocoons are often attached to vegetation near host plants or on twigs and branches of host trees. With the return of warm weather and tender leaves, adult moths emerge from the cocoon, find a mate, and deposit clusters of eggs on leaves of a wide variety of trees, vines, and shrubs. More than twenty plants are listed as hosts. 

Large feathery antennae of the male, right, enable him to detect minute amounts of sex pheromones released by the female over surprisingly large distances. Notice the much smaller and less intricate antennae of the female, left.

Hatchling caterpillars start life as dark brown or black caterpillars festooned with rows of black spines. As they grow and develop, color patterns change first to yellow bodies with black spines, and ultimately in the final instar to lime green bodies with rows of yellow, blue, orange, or red tubercles (bumps) with stout black spines. Caterpillars will gain more than a thousand times their birth weight during development. Think of it. This like an average baby turning into a three-ton adult. On second thought, don’t think of it. One has to wonder if Heimlich, the circus performer caterpillar in “A Bugs Life” was not modeled after Cecropia. Throughout most of their range from Canada to Florida there is but a single generation each year. Cecropia is believed to be one of the moths imperiled by the introduction of a parasitic fly, Compsilura concinnata, brought into the US to help manage outbreaking populations of gypsy moth. Compsilura is believed to have reduced or extirpated populations of many species of moths throughout New England.

An early morning hike along a small tributary of the mighty Susquehanna River yielded this encounter with Cecropia. Let’s hope that adventures into the suburban wilds produce more serendipitous meetings with these majestic silk moths this summer.

An early morning stroll along a lazy river revealed a mating pair of Cecropia moths. Let’s hope their connubial bliss isn’t cut short by a hungry predator or before the female has a chance to lay her eggs. Video credit: George Verdon


References used to prepare this episode include David Wagner’s suburb book “Caterpillars of Eastern North America” and Geoffrey R. Gallic’s “Featured Creatures common name: cecropia moth, cecropia silkmoth, robin moth scientific name: Hyalophora cecropia Linnaeus (Insecta: Lepidoptera: Saturniidae: Saturniinae: Attacini).” Special thanks to Sheri and Gordon Raupp and Karin Burghardt for providing spectacular images of Cecropia and to steady-handed George Verdon for providing brilliant videography for this week’s episode. 

For wonderful images of Cercropia moths and caterpillars, please visit the Maryland Biodiversity Project website at the following link.