Research: Life Cycles

The general life cycle for Drosophila melanogaster has four stages: egg, larva, pupil, and adult. If the temperature of the environment is around 21 degrees Celsius, the fruit fly will undergo the egg and larval stages for eight days, and pupa for six; their time as an adult can span up to several weeks.

The eggs hatch around twenty four hours after they are laid. The larva that emerges from the egg will have two molting periods, during which the cuticle, mouth, hooks, and spiracles are shed. The larva is called an instar during the periods of growth before and after molting. Thus, the fruit fly has three instars. The puparium develops from the third instar which becomes hard in texture and dark in color.
The puparium is where metamorphosis takes place. Just before the adult fly emerges from the puparium, the pupa darkens. Approximately 24 hours before the adult fly emerges, one can see the folded wings and the pigment of the eyes if one looks closely through the puparium.
Upon completion of metamorphosis, the adult forces its way through the operculum (anterior end) of the puparium. Initially the fruit fly appears light in color with a long abdomen and unexpanded wings. In just a few hours the fly gets darker in color, rounder in the abdomen and extends its wings.
Approximately 48 hours after emerging from the puparium, it is possible for females to start laying eggs. However, there are only 12 hours that a female can be considered virgin after emerging as an adult. After reaching this maturity, the flies are fertile for life. A female fruit fly can store sperm after a single insemination and use it for many reproductions; therefore it is important to use virgin females for genetic crosses.