Hemolymph cells, or hemocytes, derive exclusively from the mesoderm of the procephalon. After mitosis 17 (stage 11), hemocytes remain mitotically quiescent during the rest of embyogenesis. During stages 11 and 12, hemocytes slowly move out from the head, following various routes. Moving anteriorly and ventrally, they come to populate the clypeolabrum and gnathal buds. Posteriorly directed migration brings them directly into the tail end of the germ band, which is folded over the anterior part of the germ band during this stage and abuts the head region. A large number of hemocyte precursors remain in the dorsal head region. In the following stages (12-14), hemocyte precursors migrate from both ends of the embryo towards the middle. During their migration, many hemocytes differentiate. By late stage 13, approximately half of the entire population of hemocytes have differentiated into macrophages.

Many cells within the developing embryo undergo programmed cell death, the overwhelming majority during the second half of stage 11 and first half of stage 12. Shortly after the appearance of cell death figures, first macrophages become apparent. Dying cells are clearly distinguishable with the light microscope on plastic sections by their density and pronounced shrinkage. During stage 12, dead cells start accumulating in large groups in the subepidermal space of the gnathal segments and the dorsal tip of the extended germ band, where they are intermingled with macrophages.