These are encapsulated earthworm cocoons. Gardens Alive is selling them; they also sell Earthworm Food and I called today and ordered both. (Note: Gardeners Supply Company also sells the eggs in a slightly different form.)
The cocoons are Lumbricus rubellus, also sometimes called a red wiggler or a redworm. It is considered an epigeic worm, meaning that it lives in rotting organic matter, but it is often found in rich garden soil. I’m not sure what the cocoons are encapsulated in (probably a cornstarch-like coating to protect them) or what their hatch rate will be, but you can bet I’ll find out.
The earthworm food can be fed to composting worms or worms in the soil. It is, of course, not necessary to buy food for your worms. They eat garbage and dirt. But I can’t resist ordering a new earthworm product, so I’ve got three pounds of it on the way and I’ll let you know what I think of it.
This product, like most commercially sold worm foods (yes, there are a few—I have even heard a rumor that Purina makes a Worm Chow, but I’ve never seen it), contains corn meal, calcium, alfalfa, molasses, and a few other goodies that offer worms a rich source of beneficial bacteria and protein. Anything containing calcium is a special treat—it helps balance the pH of the soil (worms like a neutral or slightly alkaline soil), and when earthworms digest calcium, they help transform it into a form that is easier for plants to use.
If you’d like to make your own worm food, here’s a recipe based on the instructions that came with the first worm bin I ever bought:
Worm Fattener Recipe
1 part agricultural lime, bone meal, or powdered oyster shell (available at nurseries)
2 parts wheat or corn flour
2 parts bran or wheat meal
2 parts alfalfa meal or pellets (available at nurseries or feed stores)
2 parts chicken layer pellets
Now, I must say that I’ve never tried feeding chicken pellets to my worms. Some of them contain fish meal, and it’s a little strange to think of worms eating fish instead of the other way around. (Now that I consider it, it could be a rather satisfying feeling to give worms the final say.) But give it a try if you want—just feed them sparingly by sprinkling a thin layer on top of your worm bin or scratching it into the soil, and let me know how it goes.
Or you can skip it altogether and let them eat dirt.