A butterfly is nothing but the metamorphosed form of a caterpillar. In general, all insects, including butterflies, undergo change in their form, from an egg to adult. Although the various molts that they go through vary accordingly, the process is known as metamorphosis. A butterfly passes through four stages in its entire lifecycle; the second stage in its cycle of growth being the larva or the caterpillar stage. A caterpillar is generally herbivorous, but few species are insectivorous and entomophagous as well. It is said to be a voracious feeder and several species are notorious as agricultural pests. A caterpillar has a tubular and segmented body often accompanied with hair, which causes itching when touched. It breathes through a series of small openings along its thorax and abdomen known as spiracles. With 4000 muscles which aid in its movement, a caterpillar moves through contraction of these muscles which elongate the torso. It grows through a series of molts and each intermediate stage is known as instar. This article entails the four stages that a caterpillar undergos in its lifetime.
Stages In Life Cyle Of A Caterpillar
This is the first phase in the lifecycle of a caterpillar. An egg of a butterfly or moth is of varied shapes, such as round, cylindrical or oval. The egg is generally laid on the under surface of leaves, which, in turn, helps in obtaining food easily during the next phase. The egg is protected by a hard outer covering known as chorion, which has a thin coat of wax lining it. This prevents the egg from drying up. The egg phase continues for a few weeks in the total period of lifecycle of a butterfly. However, if the egg is laid in the chilly winter months, then it gets hatched only in spring, after going through a resting phase.
The caterpillar stage is the most active one in the entire lifecycle of a butterfly. A caterpillar is a voracious eater and generally feeds on the leaves of plants. It passes through several phases, known as instars, before reaching the next phase. In each stage, the caterpillar sheds its outer cuticle made up of chitin and protein through a process called apolysis. When it reaches the last instar phase, it begins to develop wings. By the time, last instar phase is reached; development of wings begins to take place.
The third phase or the intermediate phase is the time when it crosses the larva stage and is on the verge of becoming fully grown. During this phase, it creates a button of silk for itself, with which it fastens its body to a leaf or twig. Then, it slowly sheds its skin. A hard skin is formed under the older skin known as chrysalis. The pupa stage is one in which there is little or no movement. However, growth and differentiation continues to happen within. The adult butterfly emerges from the pupa and expands its wings by pumping haemolymph into the veins of its wings. The sea change from a pupa to butterfly is called metamorphosis.
The last phase in the lifecycle of a caterpillar is known as imago. The wings of a butterfly, after it freshly emerges from the pupa stage, takes about 3-4 hours to dry and needs to be unfolded before the butterfly can fly. It has four scaled wings, comprising of two forewings and hind wings each. An adult butterfly has six legs and the first pair is reduced in case of nymphalids. Most of the butterflies excrete excess amount of dye in colors of red, white, orange and blue, soon after hatching.