How much do you have? Can you get a cheap, used microwave and nuke the bag? Would that do the trick?

Both ideas should work. Along with letting the birds look thorough it. I do not think it would hurt the garden even with the insects alive. It is not their enviornment.

Followup post. I think the heat treatment of leaving the meal worm castings in a black covered garbage can sitting in the sun has worked because I don't see anymore live beetles, and I found a lot of dead dried up mealworms, so have started using it when planting tomatoes and peppers. I put about half to two-thirds a 3 pound coffee can of the meal worm castings in each planting hole, along with two or three shovelfuls of horse manure/wood shavings compost. I will report back later if I see any significant difference between the plants planted with meal worm castings and those I didn't use it for.

I hope all your tomatoes do good. You made lemonaid out of beetle juice. :-) With the oil hitting the east coast you may need to ship a few of those tomatoes eastward.