I have seen them chew up waxworms quite frequently.

Speaking of which, I produced my first waxworm! I had set up some cultures back in October of last year. I got two or three months per culture and nothing became of it. So in February I tried it again threw in more waxworms in to cultures that I believed to be dead. I got a few more moths this time, but eventually they died off too.
So here we are in April, I go to the Manchester Show and bought some waxworms that had not been refrigerated, hoping that these would actually lead some where. So two nights ago I finally got around to setting up completely new cultures.
I went to clear the shelf of the old ones so there would be room for the new ones. I started breaking down the old ones and thought I saw something move. So I took a little bit of the medium into the palm of my hand and a waxworm crawled out. It was an 1/8 of an inch long and I fed it to one of my Melanophryniscus stelzneri. Whoo hoo! Success!
Now the question is did come from the October moths or the February moths. I am think it had to be the latter.