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common name: eastern black swallowtail
scientific name: Papilio polyxenes asterius (Stoll) (Insecta: Lepidoptera: Papilionidae)

Introduction - Distribution - Description - Life Cycle - Hosts - Defenses - Economic Importance - Selected References

Introduction (Back to Top)

The eastern black swallowtail is one of our most common and most studied swallowtails. Although it is admired for its beauty, it is one of the very few butterflies that may occasionally be considered a pest. It has been known by a variety of other names including black swallowtail, American swallowtail, parsnip swallowtail, parsley swallowtail, celeryworm, and caraway worm (Miller 1992). Several subspecies of Papilio polyxenes that occur in Mexico, Central America and South America (Minno & Emmel 1993). Only the subspecies asterius will be covered here and, for simplicity, will be referred to as the black swallowtail even though technically the name "black swallowtail" also includes the other subspecies.

Adult female eastern black swallowtail, Papilio polyxenes asterius (Stoll), with wings spread.

Figure 1. Adult female eastern black swallowtail, Papilio polyxenes asterius (Stoll), with wings spread. Photograph by Donald Hall, University of Florida.

The genus name "Papilio" is the Latin word for butterfly. The specific epithet "polyxenes" is from Polyxena, the daughter of Priamos, King of Troy (Homer's Iliad) (Opler & Krizek 1984).

Distribution (Back to Top)

The black swallowtail is found throughout southern Canada, most of the eastern and mid-western United States west to the Rocky Mountains, and southwest into Arizona and northern Mexico. It is rare in the Florida Keys, apparently due to the absence of its carrot family (Apiaceae) hosts (Minno & Emmel 1993).

Description (Back to Top)

Adults: The adult wing spread range is 6.9–8.4 cm (Minno & Minno 1999) with females typically larger than males. The upper surfaces of the wings display sexual dimorphism. The upper surface of the wings is black with two rows of yellow spots—large and bright in males and smaller and lighter in females. The area between the rows of spots on the hind wings of females is powdery iridescent blue. The blue area in males is much less prominent. There is a conspicuous red spot with a black bulls-eye on the inner hind margin of the hind wings and an isolated yellow spot on the costa of the front wings.

The under sides of wings of males and females are virtually identical. The front wings have two rows of pale yellow spots. Hind wings have rows of bright orange spots separated by areas of powdery blue.

Adult female eastern black swallowtail, Papilio polyxenes asterius (Stoll), with wings closed.

Figure 2. Adult female eastern black swallowtail, Papilio polyxenes asterius (Stoll), with wings closed. Photograph by Donald Hall, University of Florida.

Adult male eastern black swallowtail, Papilio polyxenes asterius (Stoll), with wings spread.

Figure 3. Adult male eastern black swallowtail, Papilio polyxenes asterius (Stoll), with wings spread. Photograph by Donald Hall, University of Florida.

Adult male eastern black swallowtail, Papilio polyxenes asterius (Stoll), with wings closed.

Figure 4. Adult male eastern black swallowtail, Papilio polyxenes asterius (Stoll), with wings closed. Photograph by Donald Hall, University of Florida.

Eggs: The eggs are pale yellow and are laid on the host plants.

Eastern black swallowtail, Papilio polyxenes asterius (Stoll), egg on spotted water hemlock, Cicuta maculata L.

Figure 5. Eastern black swallowtail, Papilio polyxenes asterius (Stoll), egg on spotted water hemlock, Cicuta maculata L. Photograph by Donald Hall, University of Florida.

Larvae: Young larvae are mostly black with a white saddle. The white saddle is due to uric acid deposits that may function as antioxidant to protect larvae from phototoxic chemicals in the diet (Timmerman & Berenbaum 1999). Older larvae are green with black transverse bands containing yellow spots.

Dorsal view of a 2nd instar larva of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Head is to the left.

Figure 6. Dorsal view of a 2nd instar larva of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Head is to the left. Photograph by Jerry Butler, University of Florida.

Lateral view of a 2nd instar larva of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Head is to the left.

Figure 7. Lateral view of a 2nd instar larva of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Head is to the left. Photograph by Jerry Butler, University of Florida.

Lateral view of older larva of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Head is to the left.

Figure 8. Lateral view of older larva of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Head is to the left. Photograph by Jerry Butler, University of Florida.

Full-grown larva of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Head is to the upper left.

Figure 9. Full-grown larva of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Head is to the upper left. Photograph by Donald Hall, University of Florida.

Pupae: Larvae pupate in the typical swallowtail "head-up" position attached at the posterior end to a silk pad by the Velcro®-like cremaster and supported by a silk girdle. Pupae of the overwintering generation (short photoperiod pupae) are brown, but those of other generations may be either green with yellow markings or brown depending on the pupation substrate (Scott 1986, Hazel & West 1979).

Prepupa of the eastern black swallowtail, Papilio polyxenes asterius (Stoll), attached to silk pad with cremaster and supported by silk girdle.

Figure 10. Prepupa of the eastern black swallowtail, Papilio polyxenes asterius (Stoll), attached to silk pad with cremaster and supported by silk girdle. Photograph by Donald Hall, University of Florida.

Green pupa of the eastern black swallowtail, Papilio polyxenes asterius (Stoll).

Figure 11. Green pupa of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Photograph by Donald Hall, University of Florida.

Brown pupa of the eastern black swallowtail, Papilio polyxenes asterius (Stoll).

Figure 12. Brown pupa of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Photograph by Donald Hall, University of Florida.

Life Cycle (Back to Top)

Habitats of the black swallowtail are generally open areas, including both uplands and wet areas—wet prairies, fields, flat-woods, pine savannas, roadsides, weedy areas, and gardens (Minno et al 2005). Males perch and patrol open areas for females—often near patches of host plant (Glassberg et al 2000).

Eggs are laid singly on the host plants—usually on new foliage and occasionally on flowers. Development time is variable depending on temperature and host plant species, but generally the egg stage lasts four to nine days, the larval stage 10–30 days, and the pupal stage nine to 18 days (except for overwintering pupae). Pupae are the overwintering stage. There are two generations in northern parts of the range but at least three generations in the South (Minno et al 2005, Opler & Krizek 1984).

Carter and Feeny (1986) reported on a method for maintaining a colony of black swallowtails in the laboratory with hand-pairing of adults.

Hosts (Back to Top)

Black swallowtail caterpillars utilize a variety of herbs in the carrot family (Apiaceae) as host plants, including:

native species

introduced species

They will also eat a variety of cultivated herb Apiaceae, including:

They will also use common rue, Ruta graveolens L., in the citrus family (Rutaceae).

All plant parts of both spotted water hemlock and poison hemlock and some other wild species are extremely poisonous if eaten and may also cause contact dermatitis. Care should be exercised when handling these plants and they should never be planted as caterpillar hosts. A potion of poison hemlock was used in ancient Greece to execute prisoners and is believed to be the poison taken by Socrates. Black swallowtail caterpillars are able to detoxify the furanocoumarin chemicals (particularly the linear forms) in these and other toxic Apiaceae (Berenbaum 1981).

Plant names are from Wunderlin and Hansen (2003 or 2011) or the USDA PLANTS Database.

Mock bishopweed or herbwilliam, Ptilimnium capillaceum (Michx.) Raf., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll).

Figure 13. Mock bishopweed or herbwilliam, Ptilimnium capillaceum (Michx.) Raf., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Photograph by Donald Hall, University of Florida.

Roughfruit scaleseed, Spermolepis divaricata (Walter) Raf., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll).

Figure 14. Roughfruit scaleseed, Spermolepis divaricata (Walter) Raf., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Photograph by Donald Hall, University of Florida.

Spotted water hemlock, Cicuta maculata L., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll).

Figure 15. Spotted water hemlock, Cicuta maculata L., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Photograph by Donald Hall, University of Florida.

Water cowbane, Oxypolis filiformis (Walter) Britton, a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll).

Figure 16. Water cowbane, Oxypolis filiformis (Walter) Britton, a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Photograph by Donald Hall, University of Florida.

Queen Anne's lace, Daucus carota L., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll).

Figure 17. Queen Anne's lace, Daucus carota L., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Photograph by Donald Hall, University of Florida.

Wild parsnip, Pastinaca sativa L., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll).

Figure 18. Wild parsnip, Pastinaca sativa L., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Photograph by Donald Hall, University of Florida.

Poison hemlock, Conium maculatum L., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll).

Figure 19. Poison hemlock, Conium maculatum L., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Photograph by Donald Hall, University of Florida.

Dill, Anethum graveolens L., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll)

Figure 20. Dill, Anethum graveolens L., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Photograph by Donald Hall, University of Florida.

Sweet fennel, Foeniculum vulgare Mill., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll).

Figure 21. Sweet fennel, Foeniculum vulgare Mill., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Photograph by Donald Hall, University of Florida.

Sweet fennel (flowers), Foeniculum vulgare Mill., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll).

Figure 22. Sweet fennel (flowers), Foeniculum vulgare Mill., a host of the eastern black swallowtail, Papilio polyxenes asterius (Stoll). Photograph by Donald Hall, University of Florida.

Defenses (Back to Top)

Young larvae are bird-dropping mimics. The brindled color pattern of older larvae likely makes them cryptic while resting on the sun-dappled host plants. Pupal colors match the substrate and are cryptic.

The poisonous and distasteful pipevine swallowtail, Battus philenor (L.), is the model for a complex of black-colored Batesian mimic butterflies including the black swallowtail. The ventral wing coloration of both male and female black swallowtails is mimetic (Codella & Lederhouse 1989), but only the female is a convincing mimic when the wings are spread (Lederhouse 1995). The conspicuous yellow on the upper wings of males, which renders males relatively non-mimetic, likely functions in male-male territorial interactions (Lederhouse 1982). Both sexes spend much of their time roosting with the wings closed which maximizes the protective effects of mimicry against vertebrate predators.

All swallowtail larvae have eversible horn-like organs behind the head known as osmeteria. The osmeterium of the black swallowtail is bright yellow-orange. When threatened, larvae rear up, extrude the osmeterium, and attempt to smear the potential predator with a chemical repellent. The osmeterial repellent is effective against ants (Eisner & Meinwald 1965), but Berenbaum et al (1992) reported that soldier bugs could attack and eat larvae without evoking extrusion of the osmeteria.

Eastern black swallowtail, Papilio polyxenes asterius (Stoll), with osmeterium extruded.

Figure 23. Eastern black swallowtail, Papilio polyxenes asterius (Stoll), with osmeterium extruded. Photograph by Jerry Butler, University of Florida.

Some insect parasitoids locate their hosts by volatile chemicals in the feces (Vinson 1984). Black swallowtail larvae, like those of some other swallowtail species, throw their fecal pellets with the mandibles (Lederhouse 1990).

Economic Importance (Back to Top)

Although black swallowtail caterpillars feed on a number of cultivated plants, they are never sufficiently common to cause a problem in commercial agriculture. If control is required in home gardens, hand-picking is recommended. If hand-picking is impractical, either a foliar insecticide or the bacterial insecticide Bacillus thuringiensis provides effective control (Capinera 2001). Also, there are numerous insect predators and also wasp and fly parasitoids of the caterpillars (Capinera 2001) that provide some natural control.

Selected References (Back to Top)