Saturniids, or Giant Silkmoths, in Michigan

I have fond memories from my Missouri childhood of my father holding me up in his arms to reach a cecropia moth cocoon high up in tree branches. Each fall he would collect two or three cecropia cocoons and we would let them hatch indoors to our awe and delight to see something so exquisitely beautiful at close range. Since I have lived in Michigan, I have found only two silk moth cocoons and one cecropia caterpillar in the wild, all in my backyard in Ann Arbor. Until recently, I had only seen luna moths fluttering around lights in shopping mall parking lots. However, there are several striking examples of saturniid species native to Michigan that include: cecropia (Hyalophora cecropia), luna (Actias luna), polyphemus (Antheraea polyphemus), io (Automeris io io) and promethea (Callosamia promethea) moths. Some species of saturniids adapt well to urban environments, but sadly, saturniid populations are in decline worldwide due to loss of habitat. You might be observant enough to spot a cocoon in a tree, or encounter a caterpillar while pruning a tree or shrub, but most people never get the opportunity to see a live silkworm moth, because the vast majority of these extremely large (wingspan from 2-6 inches) and beautiful moths are nocturnal. I have yet to find an explanation as to why evolution created something so colorful that is noctural. Unlike many bird species with bright plumage, these beauties of the night certainly don't use their coloration to attract a mate. Antheraea polyphemus Saturniids use powerful pheromones for all of that. Male moths are equipped with large

feather like antennae that have receptor cells that bind to the female's pheromone. Resting male Antheraea polyphemus Aided by the wind, the male persistently follows the female's pheromone scent trail, often 3-5 miles away, through obstacles such as rain, wind and cold. A female moth emits pheromones from a special gland on the tip of the abdomen, a process called "calling". Unmated females rarely fly, but wait patiently in one spot "calling" for a potential suitor, often from the late evening till dawn. The female may attract several males but she will mate with only one. The moths actually copulate and will remain co-joined until the next evening. The pair then separates and the female will fly away to a suitable host plant to lay eggs or oviposit. It is this mating process that has allowed me to see and catch a variety of wild silkmoths here in Ann Arbor. Over the past three years I have been able to catch several male luna, promethea, polyphemus and cecropia moths by leaving a recently hatched female in a small wire cage outside at night. I am happy to say, based on my own observations, that populations of these species appear to be quite healthy here in my little corner of Washtenaw County. From pairings, I have harvested eggs and successfully raised luna, promethea and cecropia caterpillars. Rearing caterpillars requires that you have time and access to appropriate amounts of suitable hostplants for the larvae to eat. Luna and polyphemus larvae will eat walnut leaves, while cecropia and promethea larvae prefer wild continued on page 12

Washtenaw County Master Gardener Newsletter

(continued from page 11) cherry foliage. Rearing caterpillars is a fascinating project for children to watch metamorphsis through five larval stgaes (instars) to the final spinning of silk cocoons. Hyalophora cecropia larva The caterpillars are so colorful and fanciful. Cecropia caterpillars have whimsical protuberances, or knobs, on their bodies and they grow to enormous proportions of up to three inches in length.

Now that's a caterpillar! Finally, as gardeners, we should not confuse these native caterpillars with their extremely destructive, non-indigenous cousin - the infamous gypsy moth caterpillar. Fear not, these native caterpillars are rarely, if ever, destructive to your favorite trees and shrubs. References: The Wild Silk Moths of North America by Paul Tuskes et al, 1996 Wings of Paradise: The Great Saturniid Moths by John Coady, 1996 For information and livestock: http://www3.islandtelecom.com/~oehlkew http://www.insectnet.com

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