QualiCell? Drosophila S2 Cell was derived from a primary culture of late stage (20-24 hours old) Drosophila melanogaster embryos. Many features of the S2 cell line suggest that it is derived from a macrophage-like lineage. S2 cells grow at room temperature in ambient CO2 as a loose, semi-adherent monolayer in tissue culture flasks and in suspension in spinners and shake flasks.