The cheery Anise Swallowtail is a butterfly found in the western part of the continent. Anise is a plant in the parsley family, and its licorice-flavored leaves and seeds are edible. Caterpillars of this butterfly use anise, fennel, and parsley as host plants. Females lay golden-yellow spherical eggs on the leaves of the plant, which are eaten by younger caterpillars. Older ones move on to the flowers and seeds, which decreases competition between them.
A young caterpillar is mostly black with a white 'waist' band. It is studded with bristly spikes. Rows of red spots form along the 'back' and sides of the caterpillar. An older instar has alternating rings in bright green and black with bright red-orange dots sitting along each black band. The short, black bristly spikes may still be present around each black ring. The green color becomes more predominant and it is not uncommon to see pale blue rings as well. A forked, orange, fleshy 'antennae-like' appendage called an osmeterium hides on the head. This defensive organ comes out when the caterpillar is threatened, and it emits a foul odor meant to deter predators from eating it.
Look for this caterpillar along the Pacific Coast, in backyard gardens, vacant lots, and up in mountainous fields where its weedy host plants grow.©CaterpillarIdentification.org
The map above showcases (in blue) the states and territories of North America where the Anise Swallowtail Butterfly Caterpillar may be found (but is not limited to). This sort of data can be useful in seeing concentrations of a particular species over the continent as well as revealing possible migratory patterns over a species' given lifespan. Some species are naturally confined by environment, weather, mating habits, food resources and the like while others see widespread expansion across most, or all, of North America.*NOTE: States/Territories shown above are a general indicator of areas inhabited by the Anise Swallowtail Butterfly Caterpillar. Insects generally go where they please, typically driven by diet, environmental changes, and / or mating habits.