I was totally grossed out by this sight the other day. Some creature was having a great time boring inside the leaves of the Echeverias and the large-leaved Cotyledon macrantha. You can see it inside the leaf pictured at about 7 o'clock position. Fortunately it doesn't bore into the stems, only the leaves and as bad as the poor Echeveria looks, it should survive.
This is what the miscreant looks like:
Getting really fat, this seems to be a grub rather than a worm which means that it is a beetle larva, not a moth or butterfly.
I found this moth pupa under a leaf which looks a lot like it may be related to that grub, or perhaps it is just an innocent bystander. Google doesn't turn up any moths that attack succulents that have similar larvae although I did find an American Cactus Borer member of the longhorn beetle family that could be it.
What is it doing in South Africa? It could be a plant pest imported as biocontrol for one of the many invasive cactus species in our country or something that arrived in a contaminated plant and has spread.
Have any other succulent growers here had this one attack their plants?