Have you ever seen a Schaus’ Swallowtail? One of Florida’s rarest butterflies emerges from mid May to mid June in Upper Key Largo and on the offshore keys of Biscayne National Park, in the few remnant tropical hardwood hammocks left. Although once found in Miami and the Keys, this rare butterfly is limited to only a few sites today. Beautiful and graceful, the Schaus’ lives about two weeks in the wild. It was listed on the federal threatened list in April, 1976 and was moved to the endangered list in August of 1984. Droughts, hurricanes, loss of habitat and occasional freezes, among other possible threats, have reduced the population. Although it does have a flight range of 300 miles, it is seen only in tropical hardwood hammocks, much of which have been developed with the Schaus’ native habitat destroyed in the process. Mosquito spraying has been thought to reduce the population further in developed areas and some observers suspect exotic ant predators and possible parasitoids.
Left: Schaus' Swallowtail.
Right: Giant Swallowtail
The adult Schaus’ looks very similar to the Giant Swallowtail; smaller in size, more brown in color and with slight variation in its markings. One of the most obvious differences is the shape and markings on the tail.
The Schaus’ tail is bordered with pale yellow with no yellow spot in the center, whereas the Giant Swallowtail has a yellow center on the tail. Another obvious way to tell the difference is that the Schaus’ has a large orange patch on the underside (ventral side). Males have yellow tips on their antennae.
The primary host plant is torchwood (Amyris elemifera) found in tropical hardwood hammocks. Also used for food is wild lime (Zanthoxylum fagara). Listed nectar plants include cheese shrub (Morinda royoc), guava (Psidium guajava), wild sage (Lantana involcrata), wild tamarind (Lysiloma latisiliquum), blue porterweed (Stachytarpheta jamaicensis) sea grape (Coccoloba uvifera), wild coffee (Psychotria nervosa), and snow squarestem (Melanthera nivea).
Eggs are laid on the tips of the leaves of host plants usually in April. The eggs hatch in April- May. The butterfly can stay in the pupal stage from one to two years, wait for ideal conditions, then emerge. Predators include birds, ants, wasps, and lizards.
The Miami Blue Chapter of the North American Butterfly Association annually joins Tropical Audubon Society on a Saturday in May for a joint field trip to permitted areas not accessible to most people. Included is a walk into the Key Largo Hammocks State Botanical Site and areas along State road 905. It is an opportunity for you to try and catch a sighting of this rare butterfly. See the Miami Blue web site calendar (www.miamiblue.org) for details of our annual visit to North Key Largo with Tropical Audubon Society. Come join us.
We also participate in annual surveys for the Schaus' Swallowtail co-conducted by Florida's Fish & Wildlife Conservation Commission, Biscayne National Park, and our South Florida NABA chapters. Traveling NABA members might want to join us; if so, email us at firstname.lastname@example.org.
Photos courtesy of Jaret Daniels, Ph.D., and Jerry Butler, Ph.D., the University of Florida.