I now know what a byssus is thanks to this prompt and a look into Wikipedia However, not having a sea or ocean in Switzerland, I do not have a great choice to show the animals with their byssus parts. The slugs decided to help me out, as they somehow also stick to surfaces. At least when I remove them from various leaves on my plants they tend to stick to my finger with their slimy gluey foot. We are in the middle of a slug invasion at the moment, at least when it rains. The rain has now made a pause. I have now got into the routine of searching my plants every morning to remove them. I have now employed a small garden shovel to scoop them up as you can see on the photo. I have all sorts, shapes and sizes and even colours. I have discovered that they are particularly partial to basil and mint. They avoid the lavender. I have now ordered a bug shell, made of metal to place on the earth. Apparently they do not like climbing on it and it keep them away from my plants. i used to use slug pellets but they do not only kill the slugs but also some useful garden insects. Slugs are not even insects it seems, but molluscs. They are definitely on my unwanted list.