Mealworms are generally considered a occasional treat,like once a week,look at some links on feeders for more info. That being said mine go crazy for them!!! They are like (crack) for chams but not good for regular feeding!!!
But if they are appropriately sized make sure you feed them something before you feed off the worms, as I don't think they eat anything at all while they are in those cups at the store. I'm sure they (and the chameleon by proxy) would appreciate some fresh fruits or veggies.
I should have mentioned I raise my own mealworms and they are gut loaded with lots of different fruits and vegetables before they are fed to my chams. Ditto what Has already been said!!!