Ariadne Spinners was a shop in Knockturn Alley that sold spiders. It carried a number of varieties, including nocturnal, venomous, bird-eating, and the "world's largest" (possibly the giant huntsman spider). A sign on the exterior of the shop stated that these spiders were "good for pets."
Ariadne was a figure in Greek mythology. She was the keeper of the labyrinth that contained the Minotaur, and assisted the hero Theseus in navigating the labyrinth by giving him a spool of thread so he could mark the path back to the entrance. However, she was abandoned on the island of Naxos on the return journey, until she was discovered by Dionysus.