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Fig. 1. (A) Schematic of an insect eggshell, drawn from published information on
Manduca and Drosophila. Features are not to scale. From left
to right, the layers are: chorion, trabecular layer (TL), crystalline
chorionic layer (CCL), wax layer, vitelline envelope (VE), serosal cuticle
(SC), serosal membrane (SM), serosa, embryo, yolk. From the VE outwards, all
layers are in place at oviposition, having been secreted by maternal
follicular cells. By contrast, the SC and SM are secreted from the serosa,
which is derived from the blastoderm. The SC is secreted first, starting at
about 12 h after oviposition (at 24°C), followed by the SM from
23–44 h after oviposition (Lamer and
Dorn, 2001). The embryo develops closely apposed to the serosa
(rather than deep within the yolk), both before and after katatrepsis. The
yolk itself becomes cellularized in the first 12 h after oviposition
(Lamer and Dorn, 2001). (B)
Schematic of gas flux model. The model terms represent the characteristics of
five different layers or sets of layers. From left to right they are: boundary
layers around the egg or its substrate, chorion, trabecular layers, a
combination of the CCL, wax layer and VE, and all remaining interior
layers.
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