- Author Existence Failure: The first artist for the Caterpillar spinoff, Isuka Hakozaki, died in April 2013. This led to the manga being put on hiatus until Hayami Tokisada took over in January 2014.
- No Export for You: Arachnid is only available in a few asian countries. It got published in France by Soleil.
- What Could Have Been: The pilot for the Caterpillar story had a male Imomushi.
- The Wiki Rule: The Arachnid Manga Wiki.