Arachnophobia is the fear of spiders and other arachnids such as scorpions. It is a word developed from the two Greek words Arachne, "spider" and Phobos, "fear."
When Hephaestus' metal spiders attacked Percy Jackson and Annabeth Chase, Annabeth panicked. She later revealed to Percy that she had an immense fear of spiders due to her mother's history with Arachne. Percy had noted that Annabeth behaved differently when she encountered the spiders, because of her fear. She started to panic but managed to regain control of herself.