It is documented here on the wiki due to being officially-released content by Mojang Studios, even if not present in a final version.
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after mining a redstone ore
Redstone bugs spawned close to redstone which was rapidly oscillating between strengths, but could also be found spawning in strongholds.
Redstone bugs, effectively being reskined silverfish, shared all of their behavior.
|Name||Savegame ID||Numeric ID||Translation key|
Redstone bugs used the ID of silverfish, different from them only by a newly-added Color NBT, which could have any color applied to it via editing, not just the redstone shades.