Firefly (Books)

Fireflies are insects mentioned briefly in the How to Train Your Dragon Book series.

Description
Fireflies are actually a type of Beetle in the Family Lampyridae. Their wings are generally more 'leathery' than a more typical, hard-shelled beetle. Fireflies are most well known, however, for their ability to emit light from their abdomens, via a chemical reaction involving the special enzyme luciferase. In adult fireflies, the bioluminescence is thought to be involved with attracting mates, while in larvae (also called glowworms) the light may serve as a deterrent to predators. Despite being widely known for their lighting, many firefly species - especially those more active during the daytime - do not glow. Instead, they rely on chemical attractants, or pheromones, to find suitable mates.

Function
Fireflies do not have a function in the Book series.

In reality, fireflies do not have a practical use either, other than as an attractive natural light show in the evenings where they occur. Their bioluminescence has been studied extensively, however, and luciferase is used extensively in molecular biology.

How to Train Your Dragon
Fireflies are mentioned once in this Book when describing the difficulty the Green Death had catching Fireworm:

"But the Green Death had the same sort of difficulty in catching Fireworm as you might have if you tried to catch a firefly with your bare hands."

- Book 1