Even though their habitats differ, Desert Black Swallowtails are very similar to Anise Swallowtails (Papilio zelicaon). They differ in the shape of the yellow marginal spots of the forewing; roundish in the Desert Black and flat in the Anise Swallowtail. At least two, possibly three, of these butterflies were seen while hiking the Tuetonia Peak Trail and try as I might, I could never catch one at rest so I have to settle with these rapid-flutter , in-flight shots. The shape of the marginal forewing spots is clearly visible though, confirming this ID.