Mealworms are the larval stage of the darkling beetle. ... Once they hatch, mealworms molt repeatedly over the course of several months until they are about 1.37 of an inch long and are ready to pupate. They remain as pupae for about one to three weeks before emerging as adult darkling beetles, ready to eat and reproduce.

How do you stop mealworms from turning into beetles?

Keep them refrigerated

The simplest solution is keep them in a refrigerator. The mealworms prefer temperatures around 70 degrees, but you don't. At 70 degrees, this encourages the mealworms to consume rapidly, which then causes them to transition into the darkling beetle.

Do dead mealworms turn into beetles?

Don't be alarmed – the pupas might look like dead mealworms. While dormant, they are transforming into adult Darkling beetles. During this time, they do not eat. This stage will last for two to three weeks before hatching.