By Ranger Steve Mueller

Immobile and vulnerable all winter, the Giant Swallowtail waits. It has many adaptations for survival. During the winter wait, it is too cold to do anything but wait. Enclosed in a chrysalis it transforms from caterpillar to winged jewel. It transforms within its last larval skin during the fall from a full-grown caterpillar to a chrysalis in a hidden location.

Inside the jewel of a chrysalis, body tissues of the caterpillar dissolve to an apparent liquid. Primordial cells actively work to rebuild an adult body through most miraculous changes. Cool or cold weather delay completion of the work for weeks or months. In the more southern states the wait between caterpillar and adult is shortest. Warm weather arrives sooner allowing the transformation process to continue.

In Michigan it is thought that the process never completes and the butterfly freezes to death in the chrysalis before spring arrives. The result is that we have no Giant Swallowtails until some immigrate north to colonize the state with a new population.

I disagree in part with such thoughts. I have seen Giant Swallowtails year after year at Ody Brook where the host plant for the caterpillar is abundant and have found them in repeated years in other patches of Xanthoxylem americanum. In still other patches of the prickly ash, I have been unable to find the butterfly. That led me to the scientific hypothesis that some swallowtails survive in isolated patches to provide an ongoing legacy.

To further support the hypothesis, I discovered that reliable patches containing the butterfly year after year had none after a very cold winter with subzero temperatures. It took a few years before those patches supported the species again. My idea is that it took a few years for immigrants to find populations of the host plant.

When host plants are found by an adult swallowtail, it lays eggs that develop into bird turd looking caterpillars that fed on the leaves. Caterpillars pupate and develop into adults by fall to provide many beauties in landscapes with host plants. Those pupating in fall wait the long winter. Many freeze but a few might survive to maintain a population in isolated patches of prickly ash. This is still not scientifically proven.

To scientific prove my hypothesis, it is necessary to provide evidence that chrysalises survived the winter in the wild. I have not looked for or found supporting evidence. That does not mean they do not survive. It means there is no supporting evidence that some survive winter in this climate. This skeptical process is what makes scientific method so valuable and self-correcting. It dispels unsupported information that we often choose to believe because we want to or because it appears logical.

Through scientific process we learned the sun does not rise in the east and set in the west. Instead we discovered the Earth rotates to provide the illusion of sunrise and sunset.

For now, science supports that Giant Swallowtails do not survive Michigan winters. I expect any Giant Swallowtail chrysalises found this winter will be frozen. Immigrants will be essential if we are to see the species this summer. The winter provided chilling subzero temperatures in local nature niches. Maybe the deep snow covered and protected a few precious winged jewels.

Natural history questions or topic suggestions can be directed to Ranger Steve (Mueller) at odybrook@chartermi.net Ody Brook, 13010 Northland Dr, Cedar Springs, MI 49319-8433.  616-696-1753.

Nevin Mills, age 2, the grandson of Gary and Rosemary Mills, of Cedar Springs, befriended a woolly “bear” caterpillar that he named “Bob.”
This type of caterpillar is the larval form of the Isabella Tiger moth. They hatch during warm weather from eggs laid by a female moth. Mature woolly bears search for sites under bark or inside cavities of rocks or logs where they can stay the winter. (That’s why you see so many of them crossing roads and sidewalks in the fall.)
When spring arrives, woolly bears spin fuzzy cocoons and transform inside them into full-grown moths.
According to the Farmer’s Almanac, woolly “bear” caterpillars became famous when Dr. C.H. Curran, curator of insects at the American Museum of Natural History in New York City, performed an experiment at Bear Mountain State Park on the woolly “bear” caterpillars to predict the weather. From 1948 to 1956, he collected as many caterpillars as he could in a day, determined the average number of reddish-brown segments, and forecast the coming winter weather through a reporter friend at The New York Herald Tribune.
According to legend, the wider that middle brown section is (i.e., the more brown segments there are), the milder the coming winter will be. Conversely, a narrow brown band is said to predict a harsh winter. During Curran’s experiments, he found the bands to be wider, and the winters were somewhat milder. He knew, however, that he was testing a small amount of data, and it was an excuse to have fun more than anything scientific.

We recently received a photo of an unusual looking caterpillar that was found by Wendy Conely, of Solon Township. She wondered what type of caterpillar it was.

We guessed it to be a cecropia moth caterpillar, and naturalist Ranger Steve Mueller, of Cedar Springs, confirmed it is indeed a cecropia moth larva. “If it was crawling about, it is probably looking for a place to spin a cocoon,” said Steve. “It will over winter and emerge in May if kept outside. If the cocoon is kept indoors it will emerge as an adult early and will not find a mate for reproduction.”

Ranger Steve is the state coordinator for Michigan and Utah for the national database of Butterflies and Moths of North America (BAMONA), a citizen science website. He said it was a good year for the silk moths, and he received several photos of adult moths that people submitted to document the species for their county.

“When people submit a butterfly or moth record, I verify the identification and then it is posted on the national database,” he explained.

Anyone can take photos and submit them to BAMONA, no species knowledge necessary. To learn more, or to get involved, visit www.butterfliesandmoths.org.