part_of chorion formation hardening and darkening of the chorion At oviposition the eggs are soft and white but within an hour the chorion begins to darken and harden. Colour development is uniform over the entire surface of the egg, and after 4h the egg shell looks black and is relatively firm. Superficially at least this process resembles sclerotization. IDOMAL:0002102 IDOMAL:0002102 The definition concerns the eggs of Aedes aegypti. Untanned chorions separated from newly laid eggs were colourless, but when chorions were isolated after they had hardened and darkened naturally , the endochorion appeared brownish-grey and the exochorion colourless. idomal_namespace physiological process of malaria vector