Fireflies are passive light-producing Mobs that appear at night in Forest and Grassland Biomes and all the time in Caves, mainly in Mushtree Forests. They are used to make the Miner Hat and Pumpkin Lantern. Fireflies can also be used to refuel Miner Hats and Lanterns by 39%.
Standing in Firefly light resets the timer in which Charlie will attack during the night, though the light from Fireflies will disappear until the player leaves their vicinity. If the player does not have a source of fire, that player may "firefly hop" between three or four groups of Fireflies for survival during the night. This can still be dangerous, as Sanity will drop significantly.
Releasing Fireflies near a Fire Pit or other key locations in one's base camp might come in handy, as glowing light will indicate their positions in total darkness of the night.
Fireflies on the ground will take up space, so the player is unable to build in that spot unless they are caught.
In the Shipwrecked DLC, Fireflies are found in Jungle Biomes and do not appear during Hurricane Season. Fireflies can also be used to craft the Boat Lantern. Fireflies are renewable as a prize at the Slot Machine.
- Despite Maxwell's quote when examining the Miner Hat ("Eventually the Firefly will starve"), Fireflies are one of the few creatures that don't starve in the inventory.
- This is probably a reference to how every item crafted from Fireflies has limited durability.
- Before mid-June 2014, Fireflies were included in the drop table for Tumbleweed.
- Fireflies can be caught during the daytime, they only become invisible but remain present at the same place. The player can wield a Net, then press the action button when close enough to their location. Unless there is a closer object that can be interacted, Fireflies will be caught even if they are not visible.