During the August 21, 2017 total solar eclipse across the United States, males of the dusk active firefly species Photinus pyralis (L.) were observed flashing at sites experiencing the totality portion of the eclipse which formed a band 113 km wide. Observers at 10 sites from Missouri to North Carolina reported observing this flash activity across a path stretching 912 km across the states where remnant late season populations of P. pyralis were active. Possible mechanisms for triggering firefly flashing behavior are discussed in the context of a total solar eclipse.