Butterflies

They start off as an egg, which hatches into a caterpillar. The caterpillar then eats and eats before pupating within a chrysalis to emerge as the adult butterfly.

My thoughts are that the reasons for this strange metamorphosis have their roots tied to the evolution of flight.

Flight has many advantages to offer insects. It allows them to disperse widely to exploit new habitats and food sources, but this requires the dedication of a large quantity of an insect's body and energy resource.

In fact, the amount of resources the power of flight requires is so great that as far as I am aware no insect can emerge from an egg in a condition ready to fly.

They all need to feed to build the powerful flight muscles and energy source needed to take to the air.

Some insects, like the grasshopper, emerge from their eggs looking like little versions of the adults, but with only the tiniest of wing structures.

Once hatched, they eat and grow and only when they reach adulthood do they take to the air.

Other insects, such as butterflies, make use of different food sources once they have matured enough to take to the air.

They have evolved different body forms suited to the different feeding styles.

The first stage or larva is designed to consume as much food as possible to allow the insect to complete its metamorphosis into the adult as quickly as possible.

The adult, meanwhile, has to take care of the complex process of reproduction and in some cases only feeding.

The complex lifecycle has other benefits for butterflies. In temperate climates like ours, it gives the various species of butterflies options on how to best survive the winters. One strategy is to spend the winter as an egg.

As an egg, the butterfly has few needs and is virtually impervious to cold. When spring arrives, eggs hatch and the caterpillars can munch on the fresh new spring growth.

Some spend the winter as a pupa, which is a bit more risky.

This is because the pupa is not totally impervious to cold and could also prove to be a tasty meal for passing hungry animals.

The advantages are an early start to the year to take advantage of spring blooms and the possibility of raising two broods in a year.

Hibernation is also another strategy for some butterflies, like the large tortoiseshells. They ride out the worst of the winter sheltered in the nooks and crannies of trees or even in our garden sheds.

This has similar risks to the chrysalis technique, but with the advantages of being able to have an even earlier start to the year.