Bookworms eat pieces of paper in the Pixie Hollow library. They are a light green color and have yellow hairs and pink anntennae on their heads. They have yellow spots on their sides and are very fat. They walk along the shelves enjoying the tasty pages.
One specific bookworm is seen in the Pixie Hollow Library while Tinker Bell is looking for a book about wings. Tink finally finds the page she is looking for, and to her dismay, a hole is in it's center. Who did the crime? None other than than the bookworm! Guiltily, the bookworm walks away, and Tinker Bell is sad, for her plan is ruined.
The bookworms are important in the movie because without the bookworms, Tink may have been able to read the page. If she was able to read the page, then she would have been able to understand why her wings were glowing. Then, she would have never needed to meet the Keeper and she would have never met her twin sister, Periwinkle.
(above: Tink looks for a book while the bookworm walks along, eating)