Papilio polyxenes (black swallowtail )

Written By Scott Macdonald

Taxonomy & Description

  • Scientific name: Papilio polyxenes

  • Common names: Black swallowtail, American swallowtail

  • Family: Papilionidae

  • Range: Widely distributed across North America, from southern Canada through the United States and into parts of Central and South America.

  • Habitat: Open fields, prairies, meadows, roadsides, gardens, and edges of woodlands.

Ecological Role

Pollination

  • Adults are generalist nectar feeders and pollinate a wide variety of native and garden flowers.

  • They are especially attracted to composite flowers (Asteraceae), milkweeds (Asclepias spp.), and mints (Lamiaceae).

Food Web Contribution

  • Larvae: Serve as prey for birds, spiders, wasps, and tachinid flies.

  • Adults: Provide food for insectivorous birds and other predators.

  • Their presence indicates healthy populations of native umbelliferous (Apiaceae) plants.

Lifecycle

  1. Egg Stage (3–9 days)

    • Eggs are laid singly on host plant leaves.

    • Initially pale yellow, darken before hatching.

  2. Larval Stage (Caterpillar)

    • Instars: 5 stages; early instars resemble bird droppings (brown/white) for camouflage; later instars are bright green with black bands and yellow spots.

    • Duration: ~10–30 days depending on temperature.

    • Defense: Osmeterium (orange, forked gland) emits foul odor to deter predators.

  3. Pupal Stage (Chrysalis)

    • Pupates on stems or nearby vegetation.

    • Two color morphs: green or brown (camouflage to environment).

    • Overwintering occurs in this stage in northern climates.

  4. Adult Stage

    • Wingspan: 3–4.5 inches.

    • Flight period: Spring to fall; multiple broods in warmer regions.

    • Adults live 2–3 weeks, seeking nectar and mates.

Native Host Plants

Black swallowtail caterpillars specialize on plants in the Apiaceae (carrot/parsley family) and occasionally Rutaceae (citrus family). Native hosts are essential for supporting wild populations.

Key Native Host Plants (Central & Eastern North America)

  • Golden Alexander (Zizia aurea) – One of the most important native larval hosts.

  • Heart-leaved Alexander (Zizia aptera)

  • Meadow Parsnip (Thaspium trifoliatum)

  • Mock Bishop’s Weed (Ptilimnium capillaceum)

  • Water Parsnip (Sium suave)

  • Common Cow Parsnip (Heracleum maximum)

  • Angelica (Angelica atropurpurea)

Additional Native or Naturalized Hosts

  • Wild carrot/Queen Anne’s lace (Daucus carota) – naturalized, not native but widely used.

  • Fennel, dill, parsley – common garden plants that can supplement but do not replace natives.

Nectar Plants for Adults

Planting a mix of native nectar plants ensures adults have resources throughout the season:

  • Milkweeds (Asclepias spp.)

  • Purple coneflower (Echinacea purpurea)

  • Bee balm (Monarda fistulosa)

  • Blazing stars (Liatris spp.)

  • Asters (Symphyotrichum spp.)

  • Joe-Pye weed (Eutrochium spp.)

Conservation & Garden Support

  • Plant multiple native host plants in clumps to help larvae find food.

  • Avoid pesticide use; larvae are highly susceptible to insecticides.

  • Provide sunny areas with shelter from wind.

  • Include nectar plants that bloom spring through fall for adults.

  • Overwintering pupae can be left undisturbed in garden debris or stems.

Ecological Significance

  • Acts as a keystone pollinator in mixed meadow and prairie ecosystems.

  • Supports predator and parasitoid diversity.

  • Its reliance on native Apiaceae plants makes it an indicator species for the health of prairie and open meadow habitats.

1. Planting Plan (Chicago Region, Native-Focused)

Goals

  • Provide host plants (larval food) and nectar plants (adult food) throughout the growing season.

  • Mimic natural prairie/meadow edges to support black swallowtails and other pollinators.

  • Use native species from Chicago’s ecoregion (Central Tallgrass Prairie) for ecological integrity.

A. Host Plants (Larval Food)

Black swallowtail caterpillars rely primarily on native members of the Apiaceae (carrot family):

Core Larval Hosts (must-haves)

  • Golden Alexander (Zizia aurea)

    • Blooms: May–June

    • Early-season host; cornerstone for native gardens.

  • Heart-leaved Alexander (Zizia aptera)

    • Blooms: May–June

    • Thrives in part shade; complements Z. aurea.

  • Meadow Parsnip (Thaspium trifoliatum)

    • Blooms: May–June

    • Adds diversity; prefers open woodland edges.

  • Cow Parsnip (Heracleum maximum)

    • Blooms: June–July

    • Large plant; great for wetter spots.

Optional Native Hosts

  • Angelica (Angelica atropurpurea)

  • Water Parsnip (Sium suave)

B. Nectar Plants (Adult Food)

Choose plants with overlapping bloom times (spring–fall):

Spring (March–May)

  • Wild columbine (Aquilegia canadensis)

  • Golden Alexanders (Zizia aurea) – doubles as host & nectar

  • Wild geranium (Geranium maculatum)

Summer (June–August)

  • Bee balm (Monarda fistulosa)

  • Purple coneflower (Echinacea purpurea)

  • Blazing stars (Liatris spicata, L. aspera)

  • Milkweeds (Asclepias tuberosa, A. syriaca)

Fall (August–October)

  • New England aster (Symphyotrichum novae-angliae)

  • Smooth blue aster (Symphyotrichum laeve)

  • Goldenrods (Solidago speciosa, S. rigida)

C. Planting Design Tips

  • Sunny location: 6+ hours sunlight daily.

  • Group in clumps: 3–5 of each species to make finding plants easier for butterflies.

  • Layer heights: Tall nectar plants (asters, joe-pye) at back; medium (coneflowers, bee balm) mid; low (golden alexander) front.

  • Watering: Most natives tolerate drought once established; cow parsnip & water parsnip need moist soils.

  • Avoid pesticides: Even “organic” sprays harm larvae.

Example 10' x 10' Butterfly Patch

  • Host layer (center & edges): 3 Zizia aurea, 2 Thaspium trifoliatum

  • Nectar spring: 3 Aquilegia canadensis

  • Nectar summer: 4 Monarda fistulosa, 3 Echinacea purpurea, 2 Liatris spicata

  • Nectar fall: 3 Symphyotrichum novae-angliae, 3 Solidago speciosa

2. Life Cycle & Flight Period (Illinois / Great Lakes)

Black swallowtails are multi-brooded in the Midwest, with timing influenced by temperature.

Spring (April–June)

  • Overwintered chrysalides emerge in April/May.

  • Adults seek early nectar (columbine, golden alexander).

  • Egg laying begins mid-May on early host plants (Zizia spp.).

Summer (June–August)

  • 2nd and 3rd generations common.

  • Eggs hatch within 3–9 days; caterpillars feed for ~2–4 weeks.

  • Pupae form on nearby vegetation; some emerge in ~2 weeks (summer brood), others overwinter (late brood).

Fall (September–October)

  • Last adults seen late September into early October.

  • Late-season caterpillars pupate and overwinter as chrysalides.

Overwintering (November–March)

  • Chrysalides remain dormant, often camouflaged on stems or garden debris.

  • Leaving standing stalks and leaf litter through winter is critical for survival.

Chicago Flight Period Summary

  • First Adults: Mid-April

  • Peak Activity: June–August

  • Last Adults: Early October

  • Broods per year: 2–3

Extra Conservation Tips

  • Plant continuous blooms March–October.

  • Include moisture sources (shallow dish with pebbles for puddling).

  • Leave seed heads and stems standing until spring cleanup.

  • Intermix host and nectar plants for easy access.

  • Combine with other butterfly hosts (milkweeds for monarchs, violets for fritillaries) for broader habitat value.

Scott Macdonald
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Monarda fistulosa (Wild Bergamot)