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 category with domain formula_65" in. An object of formula_78 is called a "morphism from formula_4 to formula_80" or a "formula_4-costructured arrow with codomain formula_80" in. Another special case occurs when both formula_4 and formula_5 are functors with domain 1. If formula_85 and formula_86, then the comma category formula_6, written formula_88, is the discrete category whose objects are morphisms from formula_8 to formula_10. An inserter category is a (non-full) subcategory of the comma category where formula_91 and formula_92 are required. The comma category can also be seen as the inserter of formula_93 and formula_94, where formula_95 and formula_96 are the two projection