It's not a mealworm pupa that's for sure! Looks more like the Dermestid beetle grubs that sometimes come with the livefood.
Definately agree. Do your crickets come with black looking beetles as well? These are the larval stage of the beetle. They are used to cut down on cleanings in large cricket breeding facilities. I have never seen them with meal worms but they just might be easier to seperate than with the crickets. They eat all the dead things at the bottom. I wouldn't feed them to the chams, given they only eat dead and slightly decayed food.