The anise swallowtail butterfly may be native to California including the Channel Islands; although it may have moved here from back East. However, the sweet fennel that its caterpillar feeds upon is invasive. In fact, it choked off huge sections of Santa Cruz Island: achieving 50 to 90% coverage in spots. It is native to Europe: in Greek it gave its name to a famous battle, and race to commemorate the messenger: marathon. It's thought to have escaped from gardens, perhaps on the island or simply as a hitchiker from the mainland. It has the potential to increase coverage still further, as the climate changes. As I've found in my backyard, it's hard to get rid of: I don't like to use herbicides, so I usually cut it down each time it appears, and dig out what roots I can. After a few years, the roots often dry up completely. I spared this plant for the caterpillar.