Before you begin the lab today, you should learn a little about the life cycle of fruit flies. Eggs are laid and hatch into first instar larvae. These larvae feed voraciously on the culture medium provided. These first instar larvae go through several instar stages and eventually the third instar larvae crawl up the sides of the bottle away from the culture medium. There they stop and their larval cuticle hardens forming a dark brown pupa.
Metamorphosis takes place during the pupal stage.
Larvae tissues degenerate and reorganize forming an adult fly inside the pupal case. When metamorphosis is complete, the adult fly emerges from the pupal case. After the fly emerges, the wings expand and dry, the abdomen becomes more rotund, and the color of the body darkens. The tip of the abdomen is elongate and somewhat pointed in females and more rounded in males. The abdomen of the female has seven segments, whereas that of the male has only five segments.