Scanning electron microscopy of the egg-shell of the fly synthesiomyia Nudiseta (wulp)
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The ultrastructure of the egg-shell of the fly Synthesiomyia nudiseta has been studied by scanning electron microscopy. The surface of the outer chorion is highly ridged, grooved and has a reticulate appearance except at the collar surrounding the micropyle. There are few aeropyles at the antimicropylar pole. The structure of the egg-shell outside the hatching lines is composed of three layers. The outer layer consists of vertical columns that arise from the middle layer, these columns branch and anastomose at their apices in the plane of the shell and form a pentagonal and hexagonal network and that is the outer most wall of the shell. The middle layer is a coarse meshwork. The inner layer consists of vertical columns which branch to form irregular-shaped discs which vary in width. The median dorsal strip enclosed by the hatching lines is very distinct, tapering and extends from the anterior end of the micropyle region to the posterior end of the antimicropyle region of the egg. The structure of the median dorsal strip is different from that of the chorion outside the hatching lines in the outermost layer. The structure of the median dorsal strip is similar to the inner layer of the chorion outside hatching lines.