I'm a bit late to the party, but I did something very similar with good success last year. Instead of waxworms, I used the smaller calciworms (soldier fly larvae). Long term, yes, it's probably fatal to the insect, but they live and squirm long enough to be eaten. Unlike crickets, caterpillars and maggots are a little bit more... deflated/stretchable, so injecting 1ml of something isn't nearly as traumatic.