A wonderful post by the Outlaw Gardener (http://outlawgarden.blogspot.com/2016/01/wednesday-vignette_20.html) led me right out to the devil garden, because I have the same plant! This is my first winter with Acanthus sennii, and I didn't know to look for these skeletonized leaves. I've seen them referred to as both skeletons and ghosts (of leaves past). Photo placement in front of the devil duck gives a good idea just how transparent they've become, but they are still quite sturdy, especially the thorny spikes on the leaves. These skeletons still bite! In any case, this plant has earned its place in the devil garden, and then some.