There has been issues of "Dimensional Bleeding" in recent packs. Twilight Forest and Promised Lands biomes seem to hijack vanilla's sub-biome generation, causing them to appear in the Overworld.
The biome listed under your mini-map is Twilight Clearing. As above stated, those are fireflies and are biome specific. I don't know of a way to remove them outside of changing the biome (silverwood trees can change to Magical Forest). I'm not sure what other options exist to change a biome are at your disposal.
There was a solution somewhere to stop the "Dimensional Bleed", but I'm pretty sure you would need to start a new world for it to work. That said, I don't remember how to fix it. Our server has just played though.