Weevil

Best answer as chosen by Asker / Ratings
In Ocarina of Time, you get the wallet upgrades by killing Golden Skulltullas and collecting their tokens.
If you've killed all the Golden Skulltullas in a dungeon/area, then an icon will appear next to the dungeon's/area's name when you view the map.
Golden Skulltullas only come out at night. Some hide up trees, so roll into trees and see if any fall out. Drop some bugs from a bottle onto patches of soft soil and they'll also appear. Some even hide in wooden crates.
You need the Boomerang (as a kid; found inside Lord Jabu-Jabu) and the Hookshot (as an adult; found inside the Graveyard at Kakariko Village) to get tokens that are far away.

Once you kill several of them, head to Kakariko Village and enter the cursed spider house. If any of the sons have returned to normal, talk to them to get a reward.