Gem Critters

Gem Critters are harmless critters that can be caught with any Bug Net and do not normally interact with the player in any other way, except in that they can be killed by both players and enemies. They have 5 health and usually serve as ambient entities in Terraria.

Gem Critters spawn near Towns in the cavern layer and Gem Trees that can be planted with Gemcorns. Their Surface Towns coutnerpart are.

Most naturally spawned Gem Critters can be caught with a Bug Net, and carried in the player's inventory (or placed in storage). If a critter caught with any Bug Net is taken from inventory and "used" (placed), it is again released into the environment at the cursor and behaves as usual.

If critter hunting on desktop, the best way to spawn any gem critter is to make a cavern town (not underground, it is one layer deeper) with three NPCs having moved in.