Answer: Earthworms prefer cool, moist, dark locations. They were already in the soil, but several feet deep and out of sight. When you placed hay on top of the soil you created nearly perfect conditions for the worms. They migrated (or gravitated) up to the rich organic matter to feed and live. Since they shun light, they probably disappeared when you removed the hay. Earthworms push their way through soft soil and eat their way through hard soil. Their burrowing loosens soil, and allows air and water to enter, which is helpful to plant roots. Hope this demystifies things for you!
Q&A Library Searching Tips