Fly (Franchise)

Flies are seen in the Dragons: Defenders of Berk TV episode, "The Eel Effect".

Description
Flies are insects of the Order Diptera. They are characterized by only having one set of wings to fly with. They are a very diverse, wide-ranging creature, occupying many ecological niches. Depending on the species, flies may be parasitic, carnivorous, carrion eaters, dung eaters, fungus eaters, nectar eaters, and so on. They are prey for a variety of invertebrates and vertebrates alike. They are also major pollinators, after bees and other Hymenoptera species.

Function
In the How to Train Your Dragon Franchise, flies have no function for humans or dragons.

However, in reality, flies and their larval stages - called maggots - have a major impact on agriculture, both good and bad. They are used to some extent in cooking and food. Flies also can be disease carriers, but maggots can also be used beneficially in medicine. The Fruit Fly is a classic laboratory organism used in scientific studies.

Dragons: Defenders of Berk
In the episode, "The Eel Effect", Toothless (Franchise) accidentally bites and swallows a Bloodvein Eel, causing him illness. His senses are heightened to negative proportions. He is able to hear the small buzz of a distant fly as a loud bothersome noise.

As an Epithet
The term "maggot" is used occasionally in the Franchise as a derogatory term.

"Meal time, maggots!"

- Outcast jailor in "Dragon Eye of the Beholder, Part 1"

"Keep pulling, you maggots, unless you want to be giant eel chum!"

- Savage in "Gone Gustav Gone"