Embryogenesis of the honeybee apis mellifera l. (hymenoptera : apidae): An sem study

Our SEM study of honeybee, Apis mellifera (Hymenoptera : Apidae), embryogenesis is based on embryos fixed at 1 hr intervals from oviposition to hatching. Embryos of equal age showed little variation, so that staging could be based on developmental age. Our data confirm many earlier light microscopical observations, but are at variance with some others. The cytoplasmic connections between the future blastoderm cells and the central yolk system are severed only at the onset of gastrulation. The serosa derives from cells which immigrate into the dorsal strip and then join up to form a pre-serosa bordering the germ band rims. When the serosa has detached, the amnion grows out from the germ band margins and serves as a provisional dorsal epithelium right from the beginning. Germ band segmentation is followed by the transient regression of every second transverse groove (double segment pattern). The germ band flanks grow dorsally and replace the amnion a few hr before hatching (dorsal closure). The tracheal openings which form half-way between segment borders are closed temporarily by the embryonic cuticle; similar openings above the labial buds contribute to the tentorium rather than the tracheal system. Most head appendages retain bud character until long after hatching. The events observed in the SEM are linked in a diagram to the stage series based on living embryos.