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 operator Comma operator In the C and C++ programming languages, the comma operator (represented by the token codice_1) is a binary operator that evaluates its first operand and discards the result, and then evaluates the second operand and returns this value (and type). The use of the comma token as an is distinct from its use in function calls and definitions, variable declarations, enum declarations, and similar constructs, where it acts as a . The comma operator separates "expressions" (which have value) in a way analogous to how the semicolon terminates "statements," and sequences of expressions are enclosed in parentheses analogously