The segmental organization of the fruit fly (Drosophila melanogaster)

The development of a fruit fly from the fertilized
egg cell to the segmented body of the adult
organism takes nine days. The larvae hatch after
one day and pass through defined stages of
embryonic development. The embryo forms a
cocoon at five days and, after metamorphosis,
emerges as a 2 mm-long adult fly. The head of
the adult has three segments (C1–3), the thorax
three (T1–3), and the abdomen eight segments
(A1–8). A fruit fly has altogether 14 parasegments
(P1–14), each corresponding to the last
half of one and the first half of the next segment.
The segmental organization is discernible in the
larva.