Life Cycle of a Moth "Metamorphosis"
The stages of development for a moth are the same as butterflies. As with butterflies the life cycle of moths has four basic elements with minor variations for some moth species.
Moths, like butterflies, begin as an egg generally laid on the underside of host plant leaves either singly or in clusters in numbers ranging from several to 20,000. Eggs may also be burrowed in the flesh of these plants or even just laid on the ground near hosts. The host plants are located by the adults moths by their ability to identify chemical emissions produced by plants.These microscopic eggs soon hatch (in a week or less) into microscopic caterpillars who's diversity and beauty can rival that of the final stage.
As the caterpillar starts to grow it actually out grows its skin during the process. Much like a snake, they shed this skin to permit further growth. The time between these sheddings is called an "instar". To complete this stage of the journey a caterpillar generally passes through an average of five instars (but can be as many as ten) spanning two to four weeks.
Each instar can produce a visual change in the caterpillar such as different colour or the addition or disappearance of appendages.....like the disappearance of the horn on certain Sphinx caterpillars during the last instar. Identification can be quite tricky depending on the instar the caterpillar is in at the time of observation.
Once these stages of the moths development are complete the caterpillar pupates. This is achieved in several different ways. Some spin a cocoon of silk around themselves. Some gather up debris such as leaves, roll themselves up and hold it all together with silk. Still others burrow into the ground and form what is called a "cell". Sack Bearer moths build communal cases out of leaves and silk in which they overwinter. Moths will remain in this stage for as little as a few days to several months depending on the species or on the time of year that pupation occurs.
Upon emergence from their cocoon the adult moth will find a spot to hang and begin to pump up their wings and limbs in preparation for flight at which time they will seek food and/or a mate. As a matter of fact some moths, such as the Cecropia, don't even have a mouth - nourishment is not part of their agenda, they seek only to mate and have a meer ten to fifteen days to do so at which time they will die. This stage lasts from two weeks to two months for most moths.
Recently I came across this wonderful poster depicting the life cycle of the Cecropia moth. Great artwork and footnotes make this a must as part of a reference library or just to decorate your home. Click on the thumbnail below to link to Mary Walter VanSlyke's site for more information.