The Poisonous Piffleworm appears in A Hero's Guide to Deadly Dragons as an inhabitant of the Meathead Public Library. Evidently Piffleworms like chowing down on paper and have earned the nickname "bookworm."
Traits and Abilities
Poisonous Piffleworm venom is so deadly that a victim of its bite will die in about a quarter of a second. It is purple in color and acidic enough to burn stone. They have poison glands on their necks and inject the toxin via pin-point sharp fangs. The deadly venom makes up for their diminutive size: about the "size of a largish newt."
Piffleworms despise the sound of whistling. Doing so will essentially stun them for a time, as stiff as a statue.
Hiccup and friends encounter a large group of sleeping Piffleworms lining the floors of a secret cave-like exit from the Meathead Public Library. Hiccup temporarily forgets how to deal with Piffleworms, but finally remembers about whistling. Stormfly obliges them, and the group are able to sneak past the frozen Piffleworms to safety from Driller-Dragons.
- A Hero's Guide to Deadly Dragons (Book 6), Cressida Cowell. 2007.
- The Complete Book of Dragons: A Guide To Dragon Species, Cressida Cowell. 2014