In late summer and early fall, the Sachem (
Atalopedes campestris) becomes more prominent among the active skippers. Last year it was one of the last skippers still flying in October. This one is nectaring in a patch of purple loosestrife near the river. Though the flowers are pretty, it is best not to plant this since it is invasive.
Here is a view of the uppersides of a Sachem's wings. The thick black mark on the forewing is distinctive.