Flies, butterflies, caddisflies, bees, ants, beetles and a large majority of insects undergo complete metamorphosis (more than 85 per cent of species). The differences between larvae and adults are sometimes so pronounced that it can be difficult for someone who is unfamiliar with insects to know what a larva will become once it reaches adulthood.
The life cycle of holometabolous insects (those which undergo complete metamorphosis) includes four distinct stages: egg, larva (caterpillar), pupa (chrysalis) and adult.
Eggs and larval life
After mating, the female insect usually deposits her eggs in a place where the larvae can find food easily. Depending on the species, eggs are laid individually or in groups and hatch after a few days, months or even years.
Some species lay only a few eggs, while others lay hundreds or even thousands. Some insects, such as certain species of mosquitoes, can lay eggs several times over the course of a few weeks. In other species, such as social insects, females take care of eggs, clean them, protect them and feed young larvae in the nest for a certain period of time.
As with insects that undergo incomplete metamorphosis, larval life is mainly a stage of growth. Between each moult, the insect spends almost all of its time eating. Some insects eat only during this period.
The larvae of insects that undergo complete metamorphosis are often worm-shaped with or without legs. With varying degrees of mobility, they undergo a certain number of moults before they transform, not into adults, but pupae.
Pupal and adult life
Pupation is a phase of the life cycle that is unique to insects that undergo complete metamorphosis. During this stage, major internal transformations take place so that the insect can become an adult. The beginnings of wings appear at this stage. At the pupal stage, the insect does not eat and is usually almost or completely immobile.
After a period of time in the pupal stage comes the insect’s first moult, which marks the transition to adulthood. The adult insect is usually winged and very mobile. It can reproduce and ensure the continuity of the species.