“I found these (see attached video) underneath a paving slab, which was in the middle of a small 2m x 2m bed”, writes Sarah in her submission regarding the bright green worms pictured below. “I don’t think they are caterpillars. There was a big mass of them. Are they harmful? If so, could you suggest some options for dealing with them? I live in Cardiff, UK. Many thanks.” To start with, we have to point out that the video Sarah sent us (from which the screenshot below is taken) is really blurry, which makes it near impossible to make out any identifying information about the organisms other than their general shape and coloration. For that reason, we have to warn her that any suggestions we make as to their identity is not going to be 100% certain or accurate.