Metal bug

The metal bugs were a species red in colour and similar to a cat in size. They were capable of emitting ultrasonic noises.

One such bug made its way into the forcing shed of Martin Chisom in West Yorkshire, where it was able to influence the growth rate of his rhubarb, using it to constrict him. The bug declared that it claimed the Earth "by right of conquest" before redressing this statement to claim the shed. The Third Doctor negotiated a trade agreement wherein Chisom would provide manure in return for "the tenderest rhubarb in the galaxy, grown at a rate unheard of on Earth." (AUDIO: Lost in the Wakefield Triangle)