After laying fertilized eggs, butterflies often attach them to the underneath side of a leaf with an adhesive like substance to conceal them from predators as development recrudesces. The average time for an embryo to develop is 7-14 days but in exceptions where the egg is in the overwintering stage, embryos may take months to develop. During this process, the caterpillar also grows an imaginal disk for every adult body part that it will need as a mature moth or butterfly. A moth larva is sooner hatched out. It’s known as a first instar caterpillar. Caterpillars are often rapacious creatures, they feed non-stop and as they feed, they grow. But unfortunately, the growth is unilateral as the skin doesn’t grow along. They therefore have to shed their previous hatching skins but before that, they have to grow a newer larger skin that homogenizes with their current growth and then once the new skin is ready, a hormone called ecdysone is released which instructs the caterpillar to shed the older one. This process is referred to as molting. 684
The caterpillar is now in its second instar. The molting process carries on and on as most butterflies have 5-6 instars.
After the instars, a new process, the pupa stage, commences as the Prothoracicotropic hormone triggers the caterpillar to quit eating and start seeking favorable shelters from which it will pupate. This stage is usually one of great internal convulsion and transformation. It’s also driven by the ecdysone hormone which works in conjunction with another hormone called the juvenile hormone. The juvenile hormone is important in that it regulates its amounts in prior stages thus stalling the caterpillar’s metamorphosis till the time is ripe. It acts by blocking certain genes in the imaginal disks which are tiny disc shaped bags of cells that start division immediately after a chrysalis is formed. But first, it molts into a chrysalis or spins a cocoon around itself. The chrysalis is usually immobile thus camouflage is often an important note for protection against predation. In the chrysalis, an enzyme will be secreted and nearly all the larval tissue and organs (eyes, mouth, parts, legs, glands, and muscles) will be digested and reorganized into the body of the adult butterfly. The imaginal disks use the eventual protein soup formed after the disintegration of larvae tissue to fuel the rapid cell division turn into antennae, eyes, wings or other bits of the butterfly.
The process of Metamorphosis can take anywhere between a few weeks to several months depending on the butterfly species. 684