BUTTERFLIES ARE INSECTS which undergo four distinct stages of development ~ egg, larva (caterpillar), pupa (or chrysalis), and imago (butterfly). The duration of each stage, and of the whole life of the creature, varies with species. In the tropics, this development is not interrupted by cold weather or winter season. The eggs hatch several days after they are laid, and the hatchlings eat the eggshells as their first meal. The caterpillars then feed intensively on food plants, which may be a specific host, or a group of related species, or plant species in unrelated groups. The caterpillars, which have been described as eating machines, grow rapidly and moult four or five times, i.e. they shed their old and "too tight" skin to accommodate growth. The stage between moults is known as instar. Depending on species, the caterpillars attain full growth in two to eight weeks and proceed to pupate. The pupal stage lasts from one to several weeks, depending on species. Outwardly this seems a dormant stage, but dramatic changes are taking place inside the pupal case. The tissues of the organism break down and "re-constitute" to form the imago. The adult butterflies emerge through their pupal cases with limp and wet wings. These dry out in a few hours and when ready for flight they take off to seek food and mate. Butterflies may live for up to a month or more.