This is a beetle egg next to a rolled oat. Compare the size of the egg to the adult.
Larvae (mealworm) molting. This is when the mealworm sheds its outer exoskeleton in order to grow larger.
The larva on the left is about half way through the process of becoming a pupa. The one on the right is a pupa.
Adult (Darkling Beetle) in rolled oats (substrate in captivity).