Ground crawlers are pests which live on Cybertron. Resembling nothing so much as (much) smaller green versions of space slugs, they amble about on the ground minding their own business. Ground crawlers sport a number of defensive measures, being able to produce spikes, emit small bursts of energy, and even generate a protective force field around themselves. When threatened, they can burrow into the ground to escape. They're vulnerable to plasma weaponry.
Ground crawlers infested Cybertron during the Great War, though none of the participants in said war seemed too bothered by it.