Fox fire
"The origin of the northern lights has various explanations in folklore and mythology. The Finnish name for the northern lights "revontulet" is associated with the arctic fox. According to a folk tale, an arctic fox is running far in the north and touching the mountains with its fur, so that sparks fly off into the sky as the northern lights. Another version of the story says the fox throws the northern lights up into the sky by sweeping snow upwards with its tail. A more developed version then explains how moonlight is reflected from the snowflakes swept up into the sky by the fox's tail "
[Prof. Turunen on Virtual Finland]
"Folklore abounds with explanations of the origins of the spellbinding celestial lights. In Finnish they are called "revontulet", which means "fox fires" a name derived from an ancient fable of the arctic fox starting fires fire or spraying up snow with its brush-like tail. No matter that in English "foxfire" is a luminescent glow emitted by certain types of fungi growing on rotten wood. The true story is that the sun is the father of the auroras." [Joe Brady on Virtual Finland]
"Foxfire is the term for the bioluminescence created by a fungus that can grow on decaying wood in the right conditions. It is often attributed to members of the genus Armillaria, though others are reported, and as many as 40 individual species have been identified. On the suggestion of Benjamin Franklin it was used for light in the Turtle, an early submarine. In the novel The Adventures of Huckleberry Finn by Mark Twain, the characters of Huckleberry Finn and Tom Sawyer use foxfire as a source of light in order to dig a tunnel." [Wikipedia]
"Foxfire is a natural phenomenon sometimes visible at night in forests. It's caused by bioluminescent fungi in special conditions-usually on rotting bark. Foxfire is caused by a range of different species of fungi, though Armillaria mellea appears to be the most common source. This particular species emits a bluish-green glow, like glow in the dark toys. ...
Recorded observations of fungal luminescence date back to Aristotle and Pliny the Elder. Pliny identified an "Agaricke" that "grows on the tops of trees and shines at night." Renaissance philosophers wrote of `"Fungus igneus, which shines like stars with a bluish light." In folklore, "Fairy sparks" in decaying wood indicated the place where fairies held their nightly revels.
-BIOLUMINESCENCE FUNGI: LIVING LIGHT, Spores Illustrated, Conn.-Westchester Myco. Assoc., Summer 1999, via Boston Mycological Club Bulletin, Sept. 1999
...
People from many parts of the world have found uses for these natural lanterns. The Swedish historian Olaus Magnus wrote in 1652 that people in the far north of Scandinavia would place pieces of rotten oak bark at intervals when venturing into the forest. They could then find their way back by following the light.
-Elio Schaechter, from his book In the Company of Mushrooms
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In an episode of Lassie, Timmy and Boomer hunt for foxfire so as to scare the girls into not kissing them at the Hallowe'en party." [Sean B. Palmer]
(Foxfire is also apparently the name of two films, several books, a play, a town, a botanical garden, dog breeders, a bluegrass band, comic books and software- not to be confused with Firefox)