They certainly slow down in the colder weather - hiding deep down. As soon as it warms up they'll get busy again. We use old woolly jumpers (minus buttons or zips!) as worm blankets once they've broken down the one that comes with the wormery...sometimes adding a new one fills them with excitement and gets them all excitedly digesting once again.

This is a particularly good way to recycle OH's hideous Christmas pressies from his Mum