Ent 462 - Orders of Hexapoda

Complete Metamorphosis-

Notes:

There are only four stages in the life cycle of an insect with a complete metamorphosis (egg stage, larva stage, pupa stage and adult stage). As before, the term instar is used to refer to the form that an insect takes between molts and is usually used only for the larval sub-stages. However, technically, in the case of this beetle, the pupa could be called the fourth instar and the adult could be called the fifth instar!

Every group of insects with a complete metamorphosis has a unique number of larval instars. Most scarab beetles (like the May/June beetle) have only three larval instars, but a bluegrass billbug (a weevil) has five larval instars. Some moths have five larval instars in the males and six larval instars in the females! Can you guess why this would be useful for moths?

As with the chinch bug, notice the difference between the diagram and real photo of these scarab life stages. If you look at the first instar larva of the picture, it looks a lot smaller than what is represented in the diagram. The photo is of a larva that has just hatched from the egg and has not filled up the exoskeleton while the diagram is of a first instar larva that is ready to molt into the second instar!

Notice that there is no evidence of wings in the larvae, but the pupa has external wing pads and legs more of the form found in the adult.