(Chelsea Update would like to thank Tom Hodgson and the Waterloo Natural History Association for the information and the photos in this story.)
Wetlands produce more biomass (weight of plants and animals) per acre than any other habitat including tropical rain forests.
And, the Chelsea area is blessed with an abundance of wetlands on both public and private lands. Unfortunately because they are wet, they are not particularly visitor friendly most of the year. But, the winter season is the one exception. Wetlands are usually frozen solid by January and readily available for exploration until the spring thaw.
One of the easiest to wetlands to explore is the buttonbush swamp. There are many small, shallow, seasonal ponds and swales that support wetland shrubs including buttonbush.
Buttonbush gets its name from the round seed heads that adorn its bare, winter branches. They not only make buttonbush easy to recognize, but also are an important natural food source for winter birds.
During the summer, buttonbush leaves are a preferred food source for the caterpillars of two species of giant silk moth, the cecropia and promethea. By the end of the summer, these caterpillars have hidden themselves in silken cocoons that remain attached to the branches of their host until the following June. During the winter season, with careful observation, one can find these cocoons hidden among the leafless branches.
The cecropia cocoon looks like a small brown, silken bag adorned with dried, brown leaves.
The promethean cocoon is smaller and usually wrapped in a single leaf. Inside of each cocoon is a single pupa, looking a lot like a little, brown mummy; that will remain dormant until June when the beautiful adult moth will emerge.
Adult silk moths are non-feeding, living just long enough to mate and lay eggs. The cecropia is Michigan’s largest moth with a wingspan of about six inches, while the promethea is slightly smaller, but no less beautiful.
The promethean flies in late afternoon and evening, while the cecropia is strictly nocturnal.
Finding a good cecropia cocoon can be a challenge because they are often drilled open by downy woodpeckers for the nutritious pupa inside. As a result, only about one in 20 cecropia cocoons found in winter has not already suffered from woodpecker predation.
Promethea cocoons usually fair better, but are often the victims of parasitic wasps.
How can one tell if a cocoon is good? If a cecropia cocoon has a hole drilled in the side, it is definitely been visited by a woodpecker and the pupa is gone. If not, it could still be good.
To identify a good ceropia or promethean cocoon, gently shake it while holding up to your ear. If a dull thud is heard, the cocoon is good. If a dry rattling sound or no sound at all is heard it is probably not good.
Once collected from the wild, the living thing inside the cocoon is now the responsibility of the collector. Cocoons should be stored in a large ventilated jar and placed in an unheated building such as a garage or shed to prevent them from emerging too early.
Bring the container into the house in late May. Place a stick inside the container to give the emerging moth something to climb onto so that it may spread its wings properly. Release the promethea moths in late afternoon and the cecropias just before dark.
