Black Swallowtails have two forms, so they can vary in their appearance, but all have double row of yellowish spots across both sets of wings. The female yellow spots are smaller in size. They are found in grasslands, swamps, meadows, and gardens. The caterpillars are green with black stripes and orange spots. They feed on milkweed, carrot, dill, and fennel plants. In the photo clockwise are a caterpillar on dill, male, male, and female Western Black Swallowtails, all in northern Arizona.