Butterflies and moths undergo major developmental changes during their growth. The moth lay eggs, which hatch into creeping forms with chewing mouthparts. These are called as caterpillars or larvae. Incidentally, the word caterpillar is derived from two Latin words, catta pilosa, meaning hairy cat, which is quite descriptive of some kinds. During this stage the moth feeds and grows. It is only during the larval stage, that actual growth occurs, and a caterpillar’s only aim in life is to feed and store up food.
The caterpillar eats through the top of the egg, creative a hole through which it emerges. After hatching, it often eats the eggshell as its first food and this gives it invaluable nutrients. Since this is the only growing stage in a moth’s life, it has to consume as much food and store as much energy as possible. Its jaws works like scissors very rapidly and efficiently and it finishes leaf after leaf on branch after branch. The caterpillar grows rapidly so periodically it has to molt. A moth caterpillar casts off its outer skin layers five times in its life.
Although most caterpillars feed on leaves, there are strict preferences for specific host plants. These strict preferences are dictated by the chemical composition of the plant parts that the caterpillar eats. Therefore, the caterpillar feeding on a particular plant species or set of species will not eat leaves of other species. Some caterpillars may prefer slightly mature leaves, some may refuse to eat anything other than tender ones; most prefer to tender leaves but otherwise eat whichever are available on the plants where their mothers as eggs place them.
The coloring is usually such that the larvae are well camouflaged, and can thus avoid or fool predators. Sometimes there are scary looking eye designs or bristles to frighten the enemy.
When the larva is ready to pupate, it attaches itself to a spot with silk pad and cremaster. After a period of rest, it starts wriggling and makes undulating movements from tail up, until the skin bursts near the head. The skin is then pushed upwards till it gets collected near the tail. The pupa then draws it tail out and by means of some minute hooks in the cremaster, fixes it to a surface again after casting off the old skin. The pupa hang there for some days and then the adult will emerges out of that pupa for a new flying life.