The bug is actually red moss and grow bugs that form a symbiotic relationship which leads to the production of oxygen. This is used in terraforming a planet.
Each grow bug (10mu item) will improve a planet with an atmosphere by as much as a single week's output from a terraforming complex.
These can only be seeded on worlds with temperatures between 250 and 290.
A special action will release up to as much growbugs as are present.