Red-Hot Itchyworms feature in the book, A Hero's Guide to Deadly Dragons.
Red-Hot Itchyworms are unique amongst dragons because they do not possess wings, even vestigial ones. As their name suggests, they are small and worm-like and red in color.
Their primary attack and defense mechanism is biting, which is worse than being overcome by fire ants.
- "An attack by Red Hot Itchyworms feels as if every single nerve ending in your entire body is being tickled at the same time."
- ―A Hero's Guide to Deadly Dragons
The Stat and Information page in A Hero's Guide to Deadly Dragons indicates that they are "almost unbearably hot to the touch" as well as bloodsuckers, more than just a terrible bite.
Red-Hot Itchyworms are not trainable per se, but are employed by Vikings as a living guard system. Floors can be lined with the creatures, and will attack anyone who tried to walk across those floors. Dragon skin clothing does offer protection from them, however.
Red-Hot Itchyworms were strewn across the floors to guard the Meathead Public Library, in addition to the Driller-Dragons, Meathead guards, and the Hairy Scary Librarian. Later, Hiccup and Camicazi are able to tip the Hairy Scary Librarian onto the floor, where he is covered with Red-Hot Itchyworms, and can no longer remain silent in the Library. He bursts out hysterically laughing while the children and dragons make their escape.
Red-Hot Itchyworms are seen in this reference book.
- Red-Hot Itchyworms in the Hero's Guide to Deadly Dragons on the Official How to Train Your Dragon Books Website.