I have no words to describe the beauty of this time-lapse video footage of fireflies, so I'll just shut up and say you can thank photographer Vincent Brady for it, as well as Brandon McCoy for the music.
Here's the official description from its YouTube page:
Shot over the Summer of 2013 primarily in Lake of the Ozarks, MO as well as Grand Ledge, MI. The majority of the Summer I dedicated to photographing fireflies, because, well, they are just awesome. Nothing quite ends a hot and humid Summer day like the blessing of the majestic fireflies. Lake of the Ozarks is a fantastic home to the creatures. Being out on the boat and watching as they light the treeline with their all night disco party is just amazing. My good friend Brandon McCoy was nice enough to compose this track specifically for this video, which he tore-up, fantastic work on his part. This is my first complete time-lapse video, more to come!
You can get way more info about the project from Brady himself at his website here, and if you like what you see, you can actually buy prints of some of the images in the video here.