“Should the worm bed be covered with a tarp etc?” ~ Chris
It is definitely not a bad idea to cover any exposed worm beds and windrows you have with some sort of tarp.
They can provide important protection for your worms and your vermicompost. Tarps prevent rain and snow from making direct contact with the beds, but also help retain moisture. They also help to discourage birds, such as robins, from dining on your worms.
A protective tarp is especially important if you are planning to sell your castings, since heavy rains can wash away a lot of the ‘good stuff’ in the material, not to mention soaking it and thus making it difficult to screen or to separate the worms.
Not all tarps are created equal however.
You don’t want something that’s not going to allow gas exchange and/or end up baking your beds (and worms) when the sun is shining. In other words, a typical tarp you pick up at your local hardware store might not be the best choice (although it would probably work just fine in colder weather).
There are commercially available compost windrow covers.
One example is ‘Compostex Compost Covers’ .
If you are looking for an insulated bed cover you might want to try out ‘Reflectix‘.
It was actually a fellow WFS member who recommended this material to me (thanks again, George). He puts sheets of Reflectix in all his beds (leaving a 1 inch gap all around the edges) to help create a dark, humid environment for his worms.