Butterflies and moths are fairly harmless insects, but their caterpillars can do a lot of damage and have a voracious appetite. Although caterpillars are only one link in the lifecycle from egg to butterfly, at that stage, they become as much as two to three thousand times heavier!
Phase 1: from moth to egg
Butterfly and moth females lay eggs, often in groups on the leaves or other parts of plants. Some species separate them; some lay a row of eggs, while others deposit them in layers.
Every species has eggs with a characteristic shape, color, and pattern. The number of eggs also varies: one species lays dozens, the other thousands.
Phase 2: from egg to caterpillar
A small caterpillar hatches from the egg. Caterpillars are insatiable and eat almost continuously, except when they shed their skin. They cause huge damage to crops. Of some species, a few dozen caterpillars can launch such a vicious attack on a plant within twenty-four hours that it’s no longer possible to salvage it.
As the caterpillars eat more, they grow out of their skins. The number of times the caterpillar sheds its skin can vary from three to more than ten, but most species shed four or five times before pupation.
Phase 3: From caterpillar to pupa
When a caterpillar is fully grown, it stops eating and looks for a suitable place to pupate, the process by which it uses its silk glands to make a cocoon out of threads. The cocoon may be in a corner where leaves overlap or in other places. The leaf rollers use a leaf to conceal themselves and pupate. Caterpillars don’t always have to lock themselves into a cocoon: some species drop to the ground and hide in a subterranean hollow, which they reinforce with saliva and silk threads.
A pupa looks very different from a caterpillar, as it’s shorter and takes on a streamlined appearance. The skin is wrinkled at the beginning but splits over time and reveals the shiny cuticle.
A pupa doesn’t eat or move except for a small part of its abdomen. The head, proboscis, wings, and legs develop in the anterior, immobile part. The pupa eventually transforms into a butterfly.
Phase 4: from pupa to moth or butterfly
When the butterfly is fully developed, it emerges from the pupa. The butterfly first looks for a suitable place to attach itself to, and then it unfolds its wings. With barely perceptible movements of the abdomen, the butterfly uses its bodily fluids to ‘fill up’ the wing veins. This process lasts about ten to twenty minutes. The wings will harden after one to two hours, after which the butterfly can fly away into the big, wide world.
There are biological methods to effectively fight caterpillars, such as nematodes.