I know this is a really old forum, but another option for something eating the cacti is stink bugs. I don't know what part of the country you live in, but I know stink bugs are found in a very large range. I had a problem with stink bugs eating my Christmas Cacti for the longest time, but I what I have found to work is steeping crushed mint leaves in freshly boiled water for a few minutes and then spraying that on the plants every day or two will keep them off. It might work for worms as well, because there are a lot of bugs that are repelled by the smell of mint. Again I know this post is from 5 years ago, but if the problem reoccurs, you could always see if some mint works.
