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 splice Jr. advises using a semicolon, not a comma, to join two grammatically complete clauses, except when the clauses are "very short" and "similar in form", for example: Comma splices are similar to run-on sentences, which join two independent clauses without any punctuation and without a conjunction such as "and", "but" "for", etc. Sometimes the two types of sentences are treated differently based on the presence or absence of a comma, but most writers consider the comma splice as a special type of run-on sentence. According to "Garner's Modern English Usage": Comma splices often arise when writers use conjunctive adverbs (such