Earthworms are a familiar sight to gardeners and are useful in maintaing healthy garden soils;

Earthworms can be active throughout the year but are quiescent during cold or hot and dry weather. They occur in most soils, but are scarce in soils that are extremely acidic or prone to waterlogging
Earthworms eat decaying plant material and do not damage growing plants. They are important to soil structure and fertility
Some earthworms emerge at night to feed on dead plant material on the surface, and will pull fallen leaves and other plant debris into their tunnels