Forked wings and a hidden stink organ in the larva
Papilionidae packs more than five hundred fifty swallowtail species almost worldwide, including the giant birdwings of Ornithoptera. The common name nods to hindwing tails; the caterpillar’s secret weapon is the osmeterium, a forked gland that pops out when danger nears.
Linnaeus chose Papilio—Latin for butterfly—as the type genus and borrowed Greek mythic names for species epithets. Living forms usually fall into Baroniinae, Parnassiinae, and Papilioninae; an extinct Praepapilio lineage is known from middle Eocene Colorado fossils. Baronia brevicornis, confined to a tiny Mexican range, is treated as the most basal living subfamily and uniquely feeds on Vachellia in the Fabaceae. Parnassiines are largely Holarctic mountain butterflies, with Apollos famous for alpine life.
By 2005 roughly 552 extant species were tallied across tropics and temperate zones, densest between 20°N and 20°S, especially Southeast Asia. The Siberian Apollo breeds north of the Arctic Circle in northeastern Yakutia around 1,500 metres; Himalayan Apollos such as Parnassius epaphus have been recorded near 6,000 metres. Caterpillars mostly specialize on Aristolochiaceae, Annonaceae, Lauraceae, Apiaceae, or Rutaceae; some sequester aristolochic acids that make larva and adult toxic. Adults take nectar and also sip mud or manure.
Wing venation and a fused cervical sclerite help define the family, as does the eversible osmeterium on the larval prothorax. Many species practice Batesian mimicry; eastern tiger swallowtails show female-limited dark morphs controlled by a Y-linked melanism gene that tracks local color of the model Battus philenor. Predators range from red-winged blackbirds and Chinese mantises to striped skunks. Host choice even reaches kitchen gardens: Papilio polyxenes favors Queen Anne’s lace yet also carrots, parsley, dill, and fennel.
Source: Swallowtail butterfly
