Earwig

Earwigs are insects mentioned only once in the Book series, in How to Train Your Dragon.

Description
Earwigs (Order Dermaptera) are insects with a large set of pincers sprouting from their abdomins. The pincers look formidable, but are not powerful enough to harm a human. They are used for defense and capturing prey however. Earwings have small folded wings and seldom fly. Depending on the species, earwigs may eat detritus such as decaying plant matter, fresh fruit and plants, or other insects.

The common name 'Earwig' may derive from an old tale that the insects crawled into a human's ear and laid eggs. While most earwigs do like small dark places during the day, they are not parasitic or seek out ears.

Function
In the Book series, earwigs are mentioned simply as a derogatory comparison for a very small dragon.

In reality, earwigs also do not have a use for humans. Some species may be a pest of some crops, eating fruits and vegetables, but also eat plant parasites such as plant lice and aphids.

Appearances
How to Train Your Dragon