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
Comma The serial comma is also known as the Oxford comma, Harvard comma, or series comma. It is sometimes perceived as overly careful or an Americanism, but its usage occurs within both American and British English. It is called the Oxford comma because of its long history of use by Oxford University Press. Opinions among writers and editors differ on whether to use the serial comma. A majority of American style guides mandate use of the serial comma, including "The Chicago Manual of Style", Strunk and White's "The Elements of Style", and the "U.S. Government Printing Office Style Manual". The "AP