The insect life cycle and metamorphosis

Yes, it's February and in the northern hemisphere that means it's very cold outside (-22 C, -8 F this morning to be exact). Too cold for insects to do much of anything, so I have decided to take this opportunity to create a post about the insect life cycle. 

All insects begin life as an egg. This picture shows a cluster of insect eggs on the underside of a leaf. The tiny wasp on the eggs is a parasitoid looking to lay some eggs of her own inside the other insect's eggs.

 If all goes well the eggs will hatch, and insect larvae will emerge. 
Insect larvae come in many shapes and sizes.

Below are several larvae of the darkling beetle (Coleoptera:Tenebrionidae) species Zophobas morio. The smaller ones to the left are the younger larvae and the one on the far right is very close to becoming an adult insect. 
(The scale on the bottom half of the ruler is in centimeters.)

As the insect larvae grow, they must shed their hard exoskeleton in a process called ecdysis. Following ecdysis the larvae are very pale colored and they must wait for their new exoskeleton to harden. A larva in this state is referred to as a teneral larva (shown below).

Once a larva has reached its full size and the time is right it will shed its last larval exoskeleton and enter the pupal stage.

 In these two photos (below), you can see a pupa emerging from its last larval exoskeleton. 

The insect pupa is not very active as it undergoes the process 

of metamorphosis from larva to adult.

 Following pupation, the insect will undergo one final ecdysis and emerge as an adult. The adult pictured below has recently emerged from the pupal exoskeleton. Much like a recently emerged larva, the adult beetle must wait for its exoskeleton to harden.

As the exoskeleton hardens, it also darkens to black and this darkling beetle is finally ready to begin its adult insect life.

Now, I should mention that not all insects follow this progression from egg-larva-pupa-adult. This is just one example of what entomologists call complete metamorphosis (or a holometabolous life cycle). In a future post, I will try to run the hemimetabolous life cycle, but for now please feel free to peruse the Wikipedia links that I have provided. 

Thanks for reading!