Mullein moth caterpillar feeding on mullein © Shaun Wilkinson / Getty
In perhaps as many as 60 per cent of all insect species a worm-like larva transforms into a more distinctive adult.
So a larval stage must have some evolutionary advantage. It might be that larvae, many of whom burrow, can live in environments where predators struggle to co-exist, or that a mobile larva that can find its own food gets more nutrition than if it had to rely on the finite energy supply of an egg.
The most popular idea is that the strategy allows a species’ adult and juvenile forms to co-exist in the same habitat.
So a rainforest that can support both juvenile caterpillars feeding on leaves and adult butterflies feeding on flowers will be more highly populated than an imaginary one where they compete to eat flowers, for example.
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