October 3, 2019 at 10:03 am
By Wildlife Biologist Kendall Marden
It was predicted to be a less than perfect year for monarch butterflies in the northeast due to the cold, wet weather that lasted into the early summer. That may be true, but as always with wildlife, it's easy to assume something about a larger population from individual experiences that may only be true in a small area.
To me, it seems like more migrating monarchs arrived from the south which resulted in lots of caterpillars compared to the past several years. Of course, this could just be the areas I frequent. Seeing so many monarch caterpillars made me a little more likely to notice other caterpillars.
One such critter, spotted in my garden, piqued my curiosity. I often plant dill for making pickles and to dry for later use. Usually, I see a caterpillar that looks vaguely similar to the monarch cat on the plants. I knew that caterpillar didn’t look quite the same, but never took the time to figure out what sort of butterfly it would become.
The mystery finally got under my skin. After spotting it again in my garden, I identified it as a black swallowtail caterpillar. Unlike monarchs whose host plant is milkweed, black swallowtails use plants of the carrot family, including dill. While the monarchs make a marathon migration to Mexico, the burly black swallowtail bears the bitter cold and overwinters right here in Maine in its chrysalis. You read that right! They stay tucked in their thin shell all winter, through the snow and freezing temperatures, and hatch when the weather warms.
Black Swallowtails are common throughout much of Maine. We can confirm this thanks to the Maine Butterfly Survey conducted from 2007 to 2016 with the help of volunteers. While that effort is not currently active, you can help collect information on Maine's birds and bees.