Mosquito

Mosquitoes are insects that appear nominally in the How to Train Your Dragon Franchise.

How to Train Your Dragon
In the opening monologue by Hiccup, he mentions mosquitoes as possible pests in other locations, in comparison to Berk's dragons as pests.

"The only problems are the pests. (A dragon carries one sheep away. The other resumes grazing.) You see, most places have mice or mosquitoes. We have -dragons."

- Hiccup in the first movie