Well, I see this went unanswered for quite some time, but here goes anyway.
The mealies up on top of your towel are likely *not* dead, but rather about to either molt or pupate. At this time they lie around quite still in sort of a lazy J shape and the next thing you know you have a pupa or a white larva that goes and eats its head off until it's grown enough to do it again...and again...until it's ready to pupate. Once they pupate, they lie around for a while, then all of a sudden (I swear, it's like an Escher drawing) you have beetles, which start out white with a caramel head and gradually turn brown, then mahogany, then black.
The 'monster' size mealies, sadly, are usually either treated with an IGR (Insect Growth Regulator) or are a different species (Zophorbia) of beetle. Since any beetles coming from treated Tenebrio larvae are generally sterile, if they live at all, only buy these larvae if you plan to feed them out quickly.
Hope that helps, and head on over to that Mealworm Farming thread--it's HUGE but very well worth the read!