Insects that metamorphose (change form) such as beetles, wasps, butterflies and moths are the most rich in species. This is because they are able to synchronise their life cycles to the environment, including extreme conditions where animals that remain unchanged all year cannot survive.
The life cycle of insects in the order Lepidoptera is fairly uniform. Adults lay their eggs on plants or other surfaces. Larvae (caterpillars) hatch from the eggs, then grow and metamorphose from pupae into adults.
Caterpillar lifestyles are diverse and intriguing. Sometimes they feed in the open, but more often they stay hidden. Most eat the seeds, stems, galls, leaves, flowers or leaf litter of certain plants. Others consume detritus, wood, hair or wool, or are carnivorous and eat other live invertebrates. Some species hide in a larval case, while others make a covering of leaves held together by silk. Some larvae live in underground tunnels, and others bore into wood.
Māori know butterflies as pūrerehua. They commonly call their pupa tūngoungou (meaning ‘to nod’), describing the pupa’s abdomen as it bends back and forth. Pupae were sometimes part of a child’s game:
‘Children are asked by their grandparents to hold the pupa gently between the thumb and forefinger and ask it questions, such as, “Am I a good girl?” Then the pupa will wriggle its abdomen up (“Yes”) or down (“No”).’ 1
During this stage, the larva encases itself in a chrysalis or cocoon while its wings grow. It does not eat, and the period of metamorphosis may last a few days or several months. At the end of this time it emerges as an adult.
With few exceptions, adult butterflies and moths have short lives. One week is long-lived, and two weeks is the upper limit before they get worn out. Adults prolong life by sipping sugar from flowering plants – and unintentionally carry male pollen to the female parts of the flower, fertilising the plant. A minority of Lepidoptera species spend the winter in diapause – a type of hibernation. They can live as adults for up to five months.
Because their adult lives are short, they are focused on reproduction. Adults must quickly find a mate, and females must locate a place to lay their eggs.