This colorful butterfly, flitting between pickerel plants at the water edge, caught my eye while I walked around the Nature Boardwalk one afternoon. This is a female eastern tiger swallowtail. Like so many insects, these butterflies have a fascinating life cycle.
A generation of adult butterflies is called a flight. In the northern part of their range, where it gets cold as it does in Chicago, eastern tiger swallowtail butterflies have two flights each year. If you see one at this time of year, it’s likely to be a member of the second flight of the warm season. The adult females will lay a single egg on a host plant, and the egg goes on to become a caterpillar. Caterpillar hosts include birch, such as the river birch that grows at Nature Boardwalk.
When winter approaches, the caterpillars will prepare to hunker down for the cold stretch ahead. They become a chrysalis. The chrysalis is the life stage between a caterpillar and a flying, adult butterfly. In this protected case, the insect survives the cold. In the spring it will emerge as a flying butterfly like the one I photographed here, and visitors to Nature Boardwalk will once again be able to watch these graceful creatures fly from one flower to the next.
With a wingspan of up to 6.5 inches, the eastern tiger swallowtail isn’t hard to spot, but as we enter the fall season and observe cooling temperatures, it will get become increasingly rare to see these beautiful insects out and about. Be sure to come out and look for these and other butterflies at Nature Boardwalk!