Mieotic Spore
Mieotic spores (mee-oh-tik) are Tyranid creatures and are pretty much just bigger versions of Spore mines. They are completely unarmed, and their only purpose is to drift around until they find something that's not a Tyranid and then blow up in their face and shower them in acid and sharp bone and chitin fragments.
Forge World makes them and sells them in groups of three.
On the tabletop
Tyranid players, please write something about how they preform on the tabletop.