It sounds like they're starting to go into the next stage pupae I don't see anything wrong in the picture if it's taking awhile the humidity might be low or ni I getting enough moisture. I have my beetles in a bin with a oat substrate and I just separate the beetles from the oats every 4 to 6 weeks add new oats in the beetles bin and move the oats worms and eggs elsewhere. I like this way because I have different age or size meals I do the same with my super worms. I feed fresh greens every 2 to 3 days. I thought about the screen method because I read the beetles would eat the eggs or worms I produce around 3-6k worms every 4-6 weeks.

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