Mealworms prefer dark environments due to their natural behavior and ecological adaptations. There are a few reasons why they are more comfortable and thrive in darkness:

1.    Protection: In their natural habitat, mealworms live in dark and secluded places, such as under rocks, in soil, or within decaying organic matter. Darkness provides them with protection from potential predators, such as birds, reptiles, and other insects.

2.    Moisture Regulation: Mealworms have a preference for environments with stable humidity levels. Darkness helps to maintain a more consistent moisture level by minimizing exposure to direct sunlight, which can dry out their environment.

3.    Reproduction and Development: Darkness plays a role in regulating the reproductive and developmental processes of mealworms. It helps maintain the appropriate photoperiod (light/dark cycle) necessary for their growth, molting, and reproduction.

4.    Reduced Stress: Exposure to constant light can be stressful for mealworms. Darkness provides them with a sense of security, reducing stress levels and allowing them to exhibit their natural behaviors, such as feeding, burrowing, and mating.

It's important to note that while mealworms prefer darkness, they still require some exposure to light for short periods, such as during feeding and cleaning activities. However, maintaining a predominantly dark environment is beneficial for their overall well-being and breeding success.