With the lush green new fennel rising, the Anise Swallowtail butterfly has arrived; its time has come. The female lays its numerous eggs one at a time on fennel stems. The egg hatches, a caterpillar emerges, voraciously consumes fennel, grows rapidly, and goes through five stages (instars) before forming a chrysalis, from which a new butterfly emerges. Here at sea level there may be several generations, and the butterflies take to the air for several months. But all is not paradise. Numerous other insects prey on the eggs. The caterpillars can put out orange horns that emit a foul odor by way of defense. But protein-seeking birds that breed in fennel forests, such as female Red-winged Blackbirds with chicks to feed, may not care.
The Anise Swallowtail is an example of a native insect species that has become adapted to an introduced plant. The swallowtail lived in the western states long before anise (fennel) and similar plants arrived from their Mediterranean homes. The native plants on which the butterfly previously depended are now extinct or very rare. No matter, the insect has switched to the European imports and appears to be doing well.
The photo by Jutta Burger is an improvement over the two previous Anise Swallowtail photos on this site, so far.