In the Codex it says:
"...Rol D6 fro each swar produced. On a 1, the Spyder takes a wound as it is drained by the energy expenditure."
This makes it seem that the swarm is still produced on a roll of a 1, and that you can make how ever many swarms you want in one turn. I dunno. It would seem a little unfair to the other player, becasue then you would have lots of scarab swarms for free. There are a lot of unclear sentences in this codex, along with many other codexes (codi?). Ask someone at a GW store, they seem to know the rules pretty well.