Papilio polyxenes, the (eastern) black swallowtail, American swallowtail or parsnip swallowtail, is a butterfly found throughout much of North America. An extremely similar-appearing species, Papilio joanae, occurs in the Ozark Mountains region, but it appears to be closely related to Papilio machaon, rather than P. polyxenes. The species is named after the figure in Greek mythology, Polyxena (pron.: /pəˈlɪksɨnə/; Greek: Πολυξένη), who was the youngest daughter of King Priam of Troy. Its caterpillar is often called the "parsleyworm" because the caterpillar feeds on parsley.

thumb|Macro view of the parsleyworm on Anethum graveolensThe Papilio polyxenes demonstrates polyandry and a lek mating system, showing no male parental care and display sites. Females are therefore able to choose males based on these sites and males are the only resource the females find at these sites. P. polyxenes is part of the genus Papilio, which is the biggest group of the family Papilionidae. Subspecies polyxenes, once found in Cuba, is now considered likely extinct. Members of this genus typically feed on plants of the family Lauraceae, Rutaceae and Umbelliferae. They are usually found in open areas like fields, parks, marshes or deserts, and they prefer tropical or temperate habitats.

Morphology

thumb|Ventral view - female

thumb|Parsleyworm of Papilio polyxenes on [[Foeniculum vulgare]]

Eggs and larvae

Eggs are pale yellow. Young larvae are mostly black and white with a saddle, and older larvae are green with black transverse bands containing yellow spots.

Caterpillar and chrysalis

This caterpillar absorbs toxins from the host plants, and therefore tastes poor to bird predators. A section of the green pupae will turn a much darker green at the very end of the pupae stage. This color change occurs a few hours to a full day before hatching.

Sexual dimorphism

thumb|right|Papilio polyxenes female, [[Stokes State Forest, New Jersey, United States]]

The black swallowtail has a wingspan of 6.9–8.4 cm, and females are typically larger than males.

Both sexes show a red spot with a black bullseye on the inner hind margin of the hindwings and an isolated yellow spot on the front edge of the wings. The ventral side of wings of males and females are essentially identical: forewings have two rows of pale yellow spots, and hindwings have rows of bright orange spots separated by areas of powdery blue. The ventral side also acts as an effective mimic for both males and females for protection against predators.

Life cycle

alt=Papilio polyxenes caterpillar first instar on flowering Pigweed in PA|thumb|Papilio polyxenes caterpillar first instar

Females lay single eggs on host plants, usually on the new foliage and occasionally on flowers. The eggs stage lasts 4–9 days, the larval stage 10–30 days, and the pupal stage 18 days.

Feeny et al., 1985 finds that survival of eggs and larvae of P. polyxenes varies depending on the location (near Ithaca, New York) where the eggs were laid. Eggs laid on wild carrot or parsnip plants were more likely to survive to the fifth instar than were eggs laid on poison hemlock. Eggs laid on plants at elevations of above sea-level were more likely to survive than eggs laid at 120 meters above sea-level. There were also significant differences in survival rates between early and late broods in a year, and between years. In all cases, the primary cause of mortality was predation.

Emergence

Winter is spent in the chrysalis stage, and adults will emerge in the spring to seek out host plants. Adults will emerge in the mornings on a daily basis. First brood adults will fly from mid-May until late June, second brood adults will fly from early July until late August, and occasionally a partial third brood will occur that will emerge later in the season.

Food plants

Papilio polyxenes use a variety of herbs in the carrot family (Apiaceae), but will choose the food plants for their larvae based on visual and chemical variations. Host plant odor is one of the cues involved in the selection of landing sites for oviposition. The responses to these cues are innate, and feeding on a host plant as a larva does not increase the preference for that plant as an adult.

  • American angelica, Angelica atropurpurea
  • Hairy angelica, Angelica venenosa
  • Cutleaf waterparsnip, Berula erecta
  • Water cowbane, Oxypolis filiformis

Territorial defense

Male butterflies secure territories to use in mate location and courtship.

Male territories are generally of high relative elevation and topographic distinctness. This feature serves as an advantage to the lek mating system described later, as males will be concentrated in predictable locations and will be easy to encounter by females.

Lek mating

This type of territorial organization leads the black swallowtail to engage in a lek mating system.

The territory that has the most male-male encounters can be seen as being the most desirable to both males and females, and is also the territory that has the highest female visitation rate.

Similar species

  • Old World swallowtail (Papilio machaon)
  • Indra swallowtail (Papilio indra)
  • Short-tailed swallowtail (Papilio brevicauda)
  • Anise swallowtail (Papilio zelicaon)

The Papilio polyxenes was named the official state butterfly of New Jersey on January 11, 2016.

<gallery>

File:Egglaying.JPG|Laying eggs on parsley

File:Swallowtaileggs.JPG|Eggs on parsley

File:Black Swallowtail larva.jpg|First-instar caterpillar in northeast Georgia

File:Papilio polyxenes caterpillars Fifth instar.jpg|These second- or third-instar larvae in northeast Georgia still have spikes.

File:Black Swallowtail Papilio polyxenes Closeup.jpg|Late-instar caterpillar (without spikes) soon ready to pupate

File:Black-swallowtail-osmeterium.JPG|Osmeterium visible after slight provocation

File:BlackSwallowtailColorVariations.jpg|Caterpillar color variations

File:Black Swallowtail Papilio polyxenes Chrysalis.jpg|Greenish-brown chrysalis

File:Papilionidae - Papilio polyxenes.jpg|Ventral view with chrysalis

File:Papilio Polyxenes (Black Swallowtail - TX).jpg|alt=Black Swallowtail|Black Swallowtail in North Houston, TX

</gallery>

References

  • Eastern Black Swallowtail Butterfly: Large format reference quality (free) photographs Cirrus Digital Imaging
  • Ferris, CD. and Emmel, J.F. (1982). Discussion of Papilio coloro W.G. Wright (= Papilio rudkini F. and R. Chermock) and Papilio polyxenes Fabricius. Bulletin of the Allyn Museum 76: 13 pp.

This article is adapted in part from this page at the USGS Northern Prairie Wildlife Research Center.

  • "Black Swallowtail (Papilio polyxenes) (Fabricius, 1775)", Butterflies of Canada
  • eastern black swalltowtail on the UF / IFAS Featured Creatures.