Embryology of the House Fly, Musca domestica (Diptera: Muscidae), to the Blastoderm Stage

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Abstract
Serial sections of dechorionated eggs were used to study the early embryology of the house fly, Musca domestica L. The processes at 26.5°C were found not to differ essentially from those of other Diptera. Cleavage began between oviposition and 12½ minutes and continued until the cellular blastoderm was formed at between 2 and 2½ hours. In the first hour, the average rate of cleavage was 8 minutes (±5 minutes), and cleavage was synchronous until the nuclei became densely packed at the periphery. Then, an anterior-to-posterior gradient of mitosis appeared until division temporarily ceased. The cleavage nuclei were first located centrally in the anterior third of the egg, but as development proceeded, they became more evenly distributed longitudinally and away from the center, finally entering the periplasm simultaneously. Primary vitellophages, which concentrated linearly in the center of the egg, were left behind. A few secondary vitellophages appeared at the posterior pole. Pole cells were formed, but no accurate counts could be made.