What biological mechanism suppresses the yellow pigment production in female Eastern Tiger Swallowtails mimicking the Pipevine Swallowtail?

Answer

A single gene affecting dopamine levels

The switch to dark coloration in these females is genetically controlled by a single gene that regulates dopamine, which subsequently stops the production of yellow pigment.

What biological mechanism suppresses the yellow pigment production in female Eastern Tiger Swallowtails mimicking the Pipevine Swallowtail?
insectbutterflyFeaturewingSwallowtail