The Gold Worm is a critter. It is a rare, golden recolor of an ordinary Worm, with a 0.25*1/400 (0.25%) / 0.67*1/150 (0.67%) chance of spawning in place of the ordinary version. It can also be rarely obtained from opening a Can Of Worms.
As with all other golden critters, it can be caught with a Bug Net and sold for 10. It can also be used as bait, and along with the other golden bait critters, it has a bait power of 50%, the highest usable value among bait.
When thrown in shimmer, it will transform into a Gummy Worm, a consumable item that grants a permanent fishing buff.
Unlike its original counterpart, the Worm, the Gold Worm cannot be crafted into an Enchanted Nightcrawler.
It is one of the few entities that can be detected by the Lifeform Analyzer or its upgrades.
As of 1.4.4Gold Worms have an additional hidden reduced chance to be consumed, 1/20 (5%), this does not change the bait power so it does not give higher quality fishing catches compared to other gold baits.
The Bestiary entry for the Gold Worm: "Rarely, critters are found coated entirely in gold! They are worth great coin to shopkeepers and fish absolutely love golden bait!"