DRDs

What they are DRDs are: "Diagnostic Repair Darters. These are like mechanical microbes racing through Moya defending it and repairing it. A constantly moving maintenance crew, they are a finite resource. Unlike Moya, unlike the Transport Pods, DRDs are purely mechanical and can't be easily made in flight."
What they also do Threaten the crew {many episodes, but most notably They've Got a Secret},		play with the crew {Family Ties}.
How many there are Hundreds.		Which episodes they've been seen in All of them. Although they're mostly in the background.
More pictures of DRDs