3 1/8-5 1/2" (79-140 mm). Very large with rounded wings. Blackish-brown above, rimmed by yellow spots and crossed midwing by yellow band which is broken on FW but is entire on HW, where it ends in bright blue spot. Below, FW has 2 rows of yellow border-spots; HW has orange spots enclosing row of blue and gold to olive clouds and long, straight yellow bar parallel to abdomen down inner third of HW below.
Other yellow and black swallowtails are smaller, have more pointed fore wings. Schaus' and Giant swallowtails are browner, have larger wings, and more extensive yellow beneath.
Yellowish-green egg. Grass-green caterpillar, to 2" (51 mm), has double set of rimmed, orange, false eyespots with black pupils. Possibly overwinters as a caterpillar as well as a chrysalis, unusual for group. Chrysalis, to 1 5/8" (41 mm), slightly mottled, greenish. Red bay (Persea borbonia), sassafras (Sassafras albidum), and sweet bay (Magnolia virginiana) are host plants.
April-August in mid-range; February-December in up to 3 broods in Florida.
Subtropical wetlands, coastal swamps, and humid woods with standing water.
Resident from S. Maryland to S. Florida, throughout Southwest, around Gulf to S. Texas and N. Mexico. North in Mississippi Valley to Missouri.
This butterfly is the signature swallowtail of the great swamps - the Everglades, the Great Dismal, Okefenokee, Okeechobee, and Big Cypress. In common with many swamp skippers, the adults love to take nectar from pickerelweed, and they are reported to roost communally in oaks and palmettos.