Mealworm Life Cycle

Our tree frog tends to be a little shy. Or maybe he just seems that way because tree frogs are mostly nocturnal. He spends most days resting at the top edge of his habitat and comes down at night to jump in his water bath or eat a meal. 

We leave a few mealworms in a dish overnight for him to snack on. Sometimes he decides not to eat and I scoop the leftovers back up in the morning. One day this week, I was surprised to see that one of the mealworms had transformed. 

The frog's leftovers: a mealworm (top) and a pupa (bottom).

Mealworms are the larval phase of a Darkling Beetle. Just like butterflies, these beetles have a four-stage life cycle. Larvae (or caterpillars, in the case of butterflies) emerge from eggs. Next is the pupa, more commonly known as the chrysalis phase in butterflies. This is the cozy cocoon where the insect transforms their body and crawls out as an adult beetle or butterfly.

Darkling beetle lifecycle (uen.org)

The frog's leftover mealworm had become a pupa with its last larval skin shed still hanging on. We don't see this stage too often because our mealworms are kept in the fridge to slow down their growth. A mealworm can pupate in 10-12 weeks under optimal temperatures, but can last several more months in the fridge. 

This video shows some nice close-ups of the transformations a beetle experiences. Amazingly, you can even see the thin threads of their respiratory system lining that sheds with each molt!