Exact Answer: Ancestor Moth Wings can be farmed from the Spider King boss in Sekris of Mars.
In Destiny 2, Spider King is a powerful Hive enemy located in the Tangled Shore region of Mars. This boss drops a variety of loot, including the coveted Ancestor Moth Wing. The Ancestor Moth Wing allows players to craft special items and equipment that are not available anywhere else in the game. To farm this item, Guardians should head to Sekris on Mars and take on Spider King for their chance at obtaining an Ancestor Moth Wing as well as other valuable rewards from his loot pool.