I finally heard back from the owner of the Berghotel where we stayed in Elbsandsteingebirge. The park ranger who is the resident worm expert was on vacation when we first came across the Worm Monster. Now he’s back and has sent his professional opinion. He thinks the disgusting, writhing living rope that we saw is made up of Eichenprozessionsspinner, or Oak Processionary caterpillars. They too swarm in a disgusting manner, moving together in a parade of nastiness. Recent summers have seen a plague of them in Germany, possibly due to climate change. Their fine hairs cause bad allergic reactions in many people and have even caused the closing of city parks.
However, Eichenprozessionsspinner are not nearly as disgusting as the Worm Monster and I feel that this park ranger must’ve laid on the beach too long during his holiday. What we saw was some kind of larva, hairless and tiny and not nearly as orderly as the Oak Processionary caterpillars who often cross the road in a straight line (instead of a writhing, slithery mass of worms crawling over each other at an alarming speed).
Unfortunately, I don’t think we’ll ever find out what the Worm Monster is, but you can compare them to the Eichenprozessionsspinner below and decide for yourself if they are one and the same: