The synchronous firefly season begins in late May, with the prime time being late June through mid-July, and some activity continuing well into August. As Pennsylvania passes midsummer, thousands of tiny fireflies light up the night, turning the Allegheny National Forest into a fairyland. The forest located in about 110 mi (177 km) from Pittsburgh is home to 15 firefly species. Due to thick woods and plenty of watersheds, it's an ideal environment for the beautiful lightning bugs. It is also home to the unique P. Carolinus breed that was discovered here, in the Allegheny forest, in 2012. These fireflies work in synch with each other and have special flashing patterns that make them resemble holiday lights.
There are just a few sites in North America to observe synchronous fireflies, and Western Pennsylvania is one of them. Firefly is the Pennsylvania state insect. One of the most beautiful locations to watch fireflies in the Allegheny National Forest is the Tionesta Creek area, home of the Chinese lantern fireflies that emit dazzling lights, creating a unique summer night landscape.
Annual PA Firefly Festival (June 25–26, 2021)
The Pennsylvania Firefly Festival is held every year at the Black Caddis Ranch B&B near Tionesta with guided tours, music, in food. However, if you want to avoid crowds, opt for a camping site or a cabin stay so that you can spend more quality time watching the stars and fireflies.
Fireflies glow due to bioluminescence that is produced through a chemical reaction when luciferin in the firefly body mixes with oxygen. This happens only during their mating season. Then males produce flashes to send a signal to females.