Fine structure of the chorion of a moth, hyalophora cecropia.

The chorion of the moth Hyalophora cecropia has been found to consist primarily of a complex of proteins rendered insoluble by disulfide and hydrogen bonds. The bulk of the chorion is lamellate, and as in many cuticles each lamella contains a regular helicoidal series of microfibrils. The lamellar organization is disrupted in a central zone containing narrow irregular channels, and elsewhere the mature chorion is traversed by wide cylindrical channels. These open to the outer chorion surface indirectly via a porous trabeculate zone, and are distinct from the channels leading to the aeropyles, described elsewhere, in lacking cytoplasmic processes during their formation.