The big spider is the queen. You need to face her, she will lift her thorax exposing a little pink region and will then charge at you, you have to throw a stone at the queen when she exposes her pink region, then jump away as she will call more spiders. Take them out and repeat the same process on the queen. Five stones should do the trick. Jump onto the belly of the spider to use it as a jumping pad. Keep the X button pressed to gain height and then jump onto the ledge, go through the
narrow opening.