Have the Tyranids ever made use of 'bugs'?

Question

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.

Answer 1

I don't have the actual books for reference, but it seems like small bug-sized Tyranids are used in bio-weapons by other Tyranids. For example, the fleshborer beetle and flesh-worms. The Scataphagoid are apparently used for maintenance aboard the fleet. There are probably more examples, but those are the first I found.

So, small strains seem to be used as weapons or tools by larger creatures, rather than independent weapons. The in-universe reason is that they might be harder for the hive to control due to their small size/large numbers, or that they simply haven't been encountered. The out-of-universe reason for this is likely that nobody wants to move 50,000 pieces around a map(or paint them...).

Answer 2

They use microbes to alter the biosphere which they are invading in order to make its biomass more readily exploitable.

For instance, they infect the plant life to make it grow more abundantly, and they also infuse the soil with microbes to release underground organic matter, venting it to the surface.