Apparently, Andros was not a location's name. It was actually the name of the Spider God. According to legend, the ancestors of this Spider Men had followed the God of Light long during the ancient times. Because the ancestor managed to perform exceptionally meritorious services for the God of Light, he was gifted with a part of the Divinity of the Gods.
When the great war among gods had ended, the gods had fallen one after another. Andros hid himself in the Spider Kingdom and lived a quiet life ever since. Of course, this location was not named as the Spider Kingdom when he first arrived. Well, this Spider 'Brother' could not stand the loneliness for long. So he 'shot' his 'junk' into a few female spiders.
Well, one female spider could lay many eggs at a time. Not long after that, a large army of spiders spawned into being, to conquer this land. They worshipped Andros like a god ever since. They even built many temples to enshrine him.