My horned frogs all eat nightcrawlers - I just chop the worms up as needed and dust. I find that using the tail portion - say upto half an inch or so behind the clitellum - allows the worm to keep living. I use the other portion later...

As an aside, I am really impressed with the nutrient composition of earthworms (especially calcium to phosphorus ratio) - it reinforces my personal experience that they make great staples.