I've had several turn all brown and shrivel up. At first (since I'm new to mealworm farming) I thought they were turning brown because they were turning into beetles. Now that there are dozens of beetles, I've learned that they are just dead when they look like that. I've also had a couple that died while morphing from worm to pupae. I imagine there is a mortality ratio when dealing with anything like this.
In a study I was reading, it stated that if you keep the humidity in the beetle container up high, they will lay more eggs. It said you do this by placing a small container of water in with them....been thinking about doing it. Mine are in the house and the temp/humidity is pretty constant so it would be easy.