Wormery - lid on or lid off?

[Stu the fish]

Evenin' all! Been lucky to get a freebie Black plastic IBC container for a wormery - I've got a layer of loam, then the greenery. I've covered the green waste with carpet - the question I have is should I leave this open to the elements or leave the plastic lid in place to keep the rain out? or should I play it by ear and just ensure the greenery doesn't dry out? Your thoughts please?[/list]

[Monika]

Keep the lid on, Stu, the worms like it dark and damp but not sodden.