We will discuss here about the life cycle of a butterfly. The initial appearance of a butterfly after hatching from the egg is totally different from its parents. A butterfly undergoes rapid and drastic change in its life cycle, where different stages exist. This change is called metamorphosis.
Four distinct stages are found during the life cycle of a butterfly, which are Egg, Larva, Pupa and Imago.
(i) Egg: A female butterfly lays about 500—1000 eggs at a time on the leaves of their host plants. The eggs appear like poppy seeds, which remain attached to the leaf surface by means of a sticky fluid.
(ii) Larva: The larvae hatch out of the eggs within a week and start to feed on plant leaves immediately. The larva of butterfly is known as caterpillar, which appears like a worm. It also has three portions in its body — head, thorax and abdomen. The head bears a pair of horn like antennae and six pairs of simple eyes. It has very powerful chewing apparatus in its mouth. The thorax has three segments. Each segment bears a pair of small thoracic legs. The abdomen has ten segments. In third to sixth of these segments there are four pairs of soft sucker-like abdominal legs. Both thoracic and abdominal segments have breathing pores or spiracles at two sides.
A caterpillar crawls on the leaves of their host plants and feed on them. These larvae are voracious eaters and they grow very fast. During their growth they shed their old and harder skin and replace it with a new and softer one. This process is known as moulting. During larval phase it undergoes four moulting. After final moulting a caterpillar attains the largest size. At this time it intakes huge quantity of leaves. After a few more days the full grown caterpillar stops feeding and leaves the feeding site. It moves towards any small branch or petiole of leaves. It has a pair of silk glands in its body. These glands open through a tiny cone shaped structure present behind its mouth. It is called spinneret. The matured larva then starts to secrete a fluid from its silk glands through the spinneret. As soon as the fluid comes in contact with air it dries up to form very fine silken thread. With this thread larva prepares a case around ft’s body. It is called puparium or cocoon. The pupanum hangs from the branches or petioles of plants with two stronger and thicker silken threads.
(iii) Pupa: Within the puparium the internal and external organs of the larva undergo many changes to form pupa. Pupa has a compact body with the shape of a banana flower. It develops three pairs of jointed legs, folded close to its body. It also develops wing buds and compound eyes.
(iv) lmago: Within the cocoon, pupa gradually develops all features of a butterfly. At this stage it is called an imago. After completion of metamorphosis the puparium splits at its top. The young butterfly comes out through it. The wings of a young butterfly remain tightly folded. So it waits for a few hours before the wings get unfolded. As soon as it can stretch its wings, it flies away.
Butterflies visit flowers in search of nectar. When a butterfly sits on a flower, pollen grains stick to its body parts. As it goes to another flower these pollen grains get stuck on the stigma of flower, thus butterflies help in pollination.