The Southern Festoon is a swallowtail butterfly belonging to the Papilionidae family. Its life cycle is closely aligned to the herbaceous plant Aristolochia clematitis, or European Birthwort, as sole fodder plant. (In German, this butterfly's common name is in fact "Osterluzeifalter", while the herb is called "Osterluzei".) The plant's poisonous substance is larval food and remains in the organism of the adult butterfly.
The wingspan of this butterfly ranges from 46 to 56mm. Its primary colouring is light yellow with black and red markings; there is a wavy black pattern towards the edges of the wings. The Southern Festoon caterpillar may be up to 35mm long; its basic colouring varies from light brown to a light yellow with small black dots and red warts which sprout black tufts.
Zerynthia polyxena may be found throughout southern and south Eastern Europe with the exception of the Iberian Peninsula. To the east, the species may be found as far as northwest Kazakhstan. Although the butterfly usually remains at or below 1000m above sea level, it has occasionally been sighted at higher elevations up to 1700m. It prefers open environments such as meadows or bare craggy landscapes in which its forage plant, Aristolochia clematitis, thrives. The Southern Festoon likes to stay put and doesn't wander much.
Endangerment and Conservation Status
The Zerynthia polyxena is critically endangered in all of Austria; in Vienna and Lower Austria, the species is listed as Category 2, or endangered.
The straw-coloured pupae over-winter on the Birthwort plant; the adult butterfly emerges the next year in spring, usually in April or May. After mating, eggs are laid on the underside of Birthwort leaves and hatch after a week. The caterpillars are fully grown after four to five weeks. After their second moult they eat the leaves of the Birthwort, having previously only munched on the shoots and blossoms of the plant.
On sunny days it is possible to observe several young caterpillars on the upper sides of leaves. Young caterpillars already have orange spines. Grown caterpillars may usually be found on the underside of leaves. The Southern Festoon is completely dependent on the Birthwort: without it, there could be no butterfly!