We talked about this 2 or 3 months ago when I was experimenting with phoenix worms.
If the cham doesn't pierce the worms skin (ie: chew it) it won't digest.
Will Hayward suggested piercing the worms before feeding them which
works as long as the cham sees and eats them right away before they die.
This seems to be a situation exclusive to fly larvae.
Piercing it even just once with a sewing pin does the trick and it may be
worth the trouble, they are really high in calcium.
-Brad