I photographed this on the railing of my deck. It seems as if the trail of slime was swithcing on and off but as the animal uses the slime to enable it to move how is this possible? What else could have made this trail? I have a couple more photos.

When camping on Dartmoor at the start of January this year, in sub zero temperatures, my 7 year old daughter found a worm climbing up a frozen waterfall leaving a slime trail that glowed in the moonlight.

What sort of worm is this and is it common?