The firefly fairy (Angelicae lampyridae) collects coins during the day and stores them in a pouch about her waist. She takes great care to polish the coins to a most desirable shininess. At night, when she runs across a firefly trapped inside a jar by an awestruck human, she frees the captive and leaves a quarter in his or her place. Although she develops endurance and strength from carrying coins, the firefly fairy naturally possess incredible energy, most likely to match that of fireflies.
Note: I used to have an obsession with fairies and painted them (with questionable skill) and wrote up little taxonomies and scientific descriptions for each fairy species. I recently found some of these old files, so I’m going to re-post them as the season becomes appropriate. Unfortunately, the high-res original images are long gone, but I think the stories are cute.