Swallowtail butterfly tiger swallowtail), Y-linkage determines whether the females are either wild-type (yellow and black) or melanic (dark melanin replaces the yellow background). This genetic difference stems from the fact that melanism is controlled by a single gene, which controls the level of dopamine in the organism. The enzyme BAS, which assists dopamine in producing the yellow pigmentation, normally found on the wings' background, is suppressed. Without the pigmentation, the butterfly appears mostly black (the melanic form) and is a Batesian mimic of "Battus philenor", the pipevine swallowtail. There are also "Papilio glaucus" that are not wholly black; several possess an intermediate
T-comma is no official way to add keyboard support for these characters. In order to type them, one has to either install 3rd party keyboards, or use the Character Map. The Windows version of the Firefox web browser is able to generate S-comma and T-comma, even if the characters are missing from the system's fonts. Internet Explorer does not have this capability. All Linux distributions are able to correctly render S-comma and T-comma, since at least 2005. If these characters are missing from a certain font, they will be substituted with the glyph from another font. Although the X.Org Server supports