Male Synchronous Fireflies (
Photinus carolinus) will frequently synchronize their flashing patterns, as the name implies. When there are enough of them in an area, it's a truly astonishing sight to see hundreds fireflies flashing in synchrony.
Unfortunately, they only do this for a period of about 2 weeks near the beginning of June. One of the best places to witness a display is in the Great Smoky Mountains National Park. The display is so popular that the park holds a lottery each year, to determine who gets to come and see the display. (I've never won, alas.)
This year, because of the pandemic, they're going to have a "
Virtual Fireflies Event" on YouTube instead. It will be tonight (June 1st) at 8:00 p.m., Eastern Time. Hopefully, the weather and the fireflies cooperate!