The vegetable metalloids were half-plant, half-metal creatures genetically engineered on a planet in the universe of superspace.
In 2267, a war machine created by the humanoid natives was destroyed by an exploding nuclear reactor, the only part of it to survive being its mind module. It began altering the local plant life into an army of creatures in order to continue carrying out its function. The creatures attacked an expeditionary force sent from Caeminon to explore the planet's surface, killing all its members except for Rhuna, who fled. The creature pursuing her was destroyed by a landing party from the USS Enterprise led by Captain James T. Kirk, and she took them to Caeminon. The creatures, drawn by the mind module which had become part of her bracelet, broke into the city and began attacking the citizens. The Enterprise officers helped fight them off until Kirk shot the mind module with his phaser, disrupting it and stopping the creatures. (TOS comic: "Siege in Superspace")