I went and threw this thing together in about half an hour of frenzied modelling this morning from things I had lying around the bits box. I had been thinking about it for some time, but for some reason this AM I just had to go ahead and do it. The head is your standard-issue tomb spider body, the body an Alien Queen from the ill-fated Leading Edge miniatures Aliens line, the tail a coat hanger ringed by plasticard tube cut into segments, and the tail a tomb spider claw. The metal bits took some drilling to pin together; deep-ass wells with a large bore hand drill, again using coat hanger stubs cut with a pliers-wire cutter. Man, there is just something therapeutic about drilling holes in things. Anyway, I like the way it's shaping up, but God knows what I'm going to do for adornment bits. This thing feels close to the point of building itself, as so many models have done.
So according to the fluff text in the Tyranid book, this super-Zoanthrope just devours an entire Eldar craftworld, souls first. This is something the Necrons were doing to the entire galaxy before the Slann went and upgraded everyone to psykers, waaaaay back before everyone went and started using stone tools in the 40k universe. This bit of background, as well as the ribcage-motif prevalent in all Tyranid designs spurred me into this Tyranid-Necron conversion thing, which is shaping up to be the Project of 2010.
Also, I'm bloody tired of waiting for them to upgrade the Necron Codex.