Wild Indigo Duskywing, Erynnis baptisiae
This unassuming butterfly first appeared in the marsh around the year 2000. It is a prairie species formerly feeding only on Wild Indigo. Recently it developed a taste for crown vetch (used for erosion control on highways) and this has allowed it to expand its range eastward using the highways as migration corridors.
Grindstone Marsh, Hamilton, Ontario, Canada