Tenebrio molitor, commonly known as the mealworm beetle, is a species of darkling beetle. It is a small insect, measuring about 1-1.5 centimeters in length. The larvae of Tenebrio molitor, known as mealworms, are commonly used as a food source for reptiles, birds, and other animals. They have a distinct life cycle, going through several stages of growth before transforming into adult beetles.