The forest in Forest Haven is home to a species of rainbow-colored Firefly (the brighter of the two types of glowing dots flying around inside Forest Haven). You cannot catch the regular fireflies no matter how hard you try -- only these multi-colored ones.

Catch one in your bottle and bring it to the photographer on Windfall Island after you have completed his three photo challenges. In the GameCube version, the firefly is necessary to upgrade the standard Picto Box to the DX version. In the Wii U version, you can trade a firefly for a Joy Pendant by giving it to Lenzo.