In case you are wondering about the life of the fruit fly, a fruit fly has four stages in its life cycle. The four stages of a fruit fly are egg, larva, pupa, and adult stage. Usually, the egg and larval stages are eight days long and the pupal stage takes six days, therefore becoming an adult in about two weeks.
After just 24 hours after the egg has been laid, the larva hatches. The cuticle, mouth, hooks, and spiracles are shed within the two molting periods of the larva.
During the periods of growth, before and after molting, the larva is called an instar. The fruit fly has three instars and at the third instar, the puparium develops and becomes hard in texture and dark in color.
The metamorphosis phase takes place in the puparium. The pupa darkens before the adult fly emerges from the puparium. The fruit fly’s folded wings and pigment of the eyes can be seen if one looks closely through the puparium just 24 hours before the adult fruit fly emerges.
The adult forces its way through the anterior end or operculum of the puparium upon the completion of metamorphosis. The fruit fly appears light in color having a long abdomen and unexpanded wings initially. And in just a few hours, the fruit fly extends its wings, has a rounder abdomen, and the fly gets darker in color.
It is already possible for the females to start laying eggs just around 48 hours after the fly emerges from the puparium. The flies are fertile for life after reaching its maturity and a female fruit fly can store the sperm after a single insemination to be used for many reproductions. For this reason, the use of virgin females for genetic crosses is important. There are only 12 hours that the female fruit fly can be considered as a virgin after it emerges as an adult.