In any novels or any official material, have the Tyranids ever used anything 'bug' sized like a cockroach or even smaller like an ant?
Tyranids obviously evolve after consuming biomass, but they also use hordes of their smaller creatures like Termagants. I wondered if they'd ever used any tiny organisms, I know one would be easy to stamp on, but thousands of them could quickly overwhelm guardsmen etc, and even perhaps get into gaps in tougher armour such as that of a Space Marine.
A real world example might be like ants taking on a crab where they eat out the eyes and then slowly take it apart from the insides. I can understand from a physical game point of view nobody wants to paint 50,000 'ants' for one base. But it always seems like Tyranids evolve bigger when smaller might be better.