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
Serial comma Serial comma In English language punctuation, a serial comma or series comma (also called an Oxford comma or a Harvard comma) is a comma placed immediately before the coordinating conjunction (usually "and" or "or") in a series of three or more terms. For example, a list of three countries might be punctuated either as "France, Italy,and Spain" (with the serial comma), or as "France, Italyand Spain" (without the serial comma). Opinions among writers and editors differ on whether to use the serial comma, and usage also differs somewhat between regional varieties of English. In American English, not using a serial