Also called Euros or European nightcrawlers used for composting and as feeders for fish, birds, amphibians and reptiles.
They can be used for composting in worm bins alone or with others like red wigglers. I use them has they work on coarser materials like banana stems and coffee filters.
Some add them to large plant pots or raised beds where they add foods which they process into nutrition as they aerate the soil.
They can be easily maintained in a small tote in damp coconut core and fed produce scraps or grains such as cornmeal as a long-lasting food for your pet.
A half pound which is a cup of just worms numbering about 300 is $30.
A pound is 50.
More info on a Facebook gardening group Tim's plants produce and worms.