The Shapeshifting Spider of Japan

Johogumo is a class of legendary ghosts and monsters rooted in Japanese folklore. The first written accounts of the creature date back to the Edo period, though word of its exploits most likely existed in oral tradition even before that. Like many mythological spiders, it can change between a spider form and that of a beautiful, enticing woman. All one needs to do to see if a woman is a Johogumo is to place her in front of a mirror while she's in her human form.