September 2023 Plant Availability

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Greetings,

If you follow us on instagram or facebook then you may know that it has been a prosperous summer for Swallowtail caterpillars and butterflies here at the nursery. Swallowtails are some of the coolest critters that we get to encounter among our plants, so this month we’re highlighting the Swallowtail species commonly found throughout the Bay Area and some of the California native plants they rely on– including larval host plants for the caterpillars and nectar sources for the adult butterflies. We hope you enjoy reading, learn something new, and feel inspired to create habitat for Swallowtails in your community 🙂

Swallowtail Specifics: Who, What, Where, Why?

The Swallowtail butterfly family, Papilionidae, consists of at least 550 species, spanning every continent except for Antarctica. The majority of Swallowtail species are found in tropical areas, but there are about 30 species found in the United States, ~10 of which are native to California. Swallowtails are named for the tail-like extensions on the hind wings of many (but not all) Papilionidae species, which resemble the forked tails of Swallows.

Like all butterflies and moths, Swallowtails undergo complete metamorphosis with 4 distinct phases in their life cycle: egg, larva (caterpillar), pupa (chrysalis), and adult (butterfly). Predation and parasitism of butterflies are high at all stages of development, so only a small portion survive to adulthood. This is normal! In each phase of their life cycles, butterflies are an integral part of the food web. They provide food for a variety of other animals, such as birds, bats, lizards, mice, spiders, and more! Swallowtails in particular have a ton of really remarkable adaptive strategies for survival despite being somewhat low on the food chain.

Swallowtail Survival Strategies: Protection Against Predation

California Pipevine Swallowtail eggs on a new Aristolochia californica leaf

Eggs

When ovipositing (laying eggs), adult female Swallowtail butterflies use their chemical senses to identify appropriate host plants… they drum on plants to “taste” their juices using chemical sensors on the back of their legs! They also preferentially select egg-laying sites on the leaves of their host plants using visual cues such as height, flatness, green reflectance, brightness, etc. (Nagaya et. al. 2001).

Larvae (Caterpillars)

All Swallowtail larvae possess a peculiar orange structure on their heads called an osmeterium, which is a forked horn-like scent gland that they puff out through a slit in their thorax when disturbed or attacked. The osmeterium secretes a powerful smelling liquid to deter ants and parasites.

The caterpillars of several Swallowtail species are masters of camouflage and mimicry, usually changing color and patterns drastically between instar stages. Species such as the Anise Swallowtail are black with white spots or bands to camouflage them as bird droppings. Many species change color as the larva transition through instar stages to bright shades of green with black or yellow stripes and orange spots, which mimic the colorful warning of other species that are poisonous if eaten.

Caterpillars of species such as the Western Tiger Swallowtail and Pale Swallowtail have large false “eye” spots on the sides of their heads that resemble snake heads or the eyes of larger animals to deter would-be predators.

Some species, like the Pipevine Swallowtail for example, actually do become poisonous by accumulating toxic compounds as they eat the leaves of their host plants. These caterpillars display bright orange to red tubercles (fleshy spines) along their bodies to warn against their toxicity. It’s best not to handle Pipevine Swallowtail larvae, as the black tubercles along their sides are where they store the toxic aristolochic acid from the Dutchman’s Pipe (Aristolochia californica) plant and can cause a rash if they touch your skin!

Anise Swallowtail larva showing its osmeterium

Young Anise Swallowtail larva disguised as a bird dropping

California Pipevine Swallowtail larva with black and orange tubercles

Pupae (Chrysalids)

Since the chrysalis stage in a Swallowtail’s life can be particularly vulnerable for them, most have evolved top-tier camouflage skills. The pupae of some species like the California Pipevine Swallowtail (pictured below) are expertly disguised as the living or dead leaves of their host plant depending on the look of their surroundings and the temperature. There is evidence to suggest that while they are preparing to pupate, the caterpillars can detect the colors around them with photoreceptors, which trigger or inhibit the release of a hormone that controls pupal coloration– high levels of the hormone produce a brown pupa, and low levels produce a green pupa.

Adults (Butterflies)

The hind wing “tails” characteristic of most Swallowtails have evolved independently multiple times among a wide variety of butterfly and moth species. It was previously unknown why, but a recent study by Chotard et. al. (2022) found evidence that wing tails on butterflies serve as attack deflection for birds, such that birds are drawn to the wing tails and are more likely to attack them rather than more vital body parts. Chotard and her colleagues also found that the hind wing tail is the most fragile part of the wing, and therefore it is likely the most apt location to break off in a hungry bird’s beak– similar to the strategy that some lizards use when sacrificing their detachable tails to predators in order to survive attacks.

Common Swallowtail Species of the Bay Area

Pipevine Swallowtail

(Battus philenor)

Caterpillar Host Plant: Dutchman’s Pipe (Aristolochia californica)
Nectar Plants: Thistles (Cirsium), lilac (Ceanothus), Azaleas (Rhododendron occidentale), Verbenas, Lupines, California Buckeye (Aesculus californica), Yerba Santa (Eriodictyon californicum)
Habitat: Wide variety of open habitats, open woodlands, and woodland edges
Life History: females lay batches of eggs on underside of host plant leaves. Caterpillars feed in small groups when young but become solitary when older. Sometimes overwinter as chrysalis.
Flight: In the east the adults fly primarily in late spring, but in California they are more common in late summer and fall where lack of freezing temperatures permit.

Anise Swallowtail

(Papilio zelicaon)

Caterpillar Host Plants: Many members of the parsley family (Apiaceae) such as Angelica spp., Yampah (Perideridia) spp., Cow Parsnip (Heracleum maximum), and Biscuitroot (Lomatium) spp.
Nectar Plants: Adults like lots of different flowers in a native garden
Habitat: Bare hills, mountains, gardens, fields, vacant lots, and roadsides
Life History: Males perch on hilltops and patrol for receptive females. Females lay eggs singly on host plant leaves and flowers. Young caterpillars eat leaves while older ones eat flowers. Chrysalids hibernate.
Flight: one flight from April – July

Pale Tiger Swallowtail

(Papilio eurymedon)

Caterpillar Host Plants: Trees and shrubs in Rosaceae, Rhamnaceae, and Betulaceae families including cherry (Prunus spp.) Coffeeberry (Frangula californica; formerly known as Rhamnus californica), and Ash (Fraxinus spp.).
Nectar Plants: California Buckeye (Aesculus californica), Yerba Santa (Eriodictyon californicum)
Habitat: Foothills, open woodlands, chaparral, streamsides
Life History: Males perch and patrol for receptive females. Females lay eggs singly on host plant leaves. Caterpillars feed on leaves and rest on silken mats in shelters of curled leaves. Pupae hibernate.
Flight: One flight from April – July, many flights in southern California from March – August

Image courtesy of Wikimedia Commons

Western Tiger Swallowtail

(Papilio rutulus)

Caterpillar Host Plants: Cottonwoods and Aspen (Populus), willows (Salix), wild cherry (Prunus), and ash (Fraxinus)
Nectar Plants: Thistles (Cirsium), Abelia, California Buckeye (Aesculus californica), Yerba Santa (Eriodictyon californicum)
Habitat: woodlands near rivers and streams, wooded suburbs, canyons, parks, roadsides, and oases
Life History: Males patrol canyons or hilltops for receptive females. Females lay eggs singly on the surface of host plant leaves. Caterpillars feed on leaves and rest on silken mats in shelters of curled leaves. Chrysalids hibernate.
Flight: one flight from June-July

Feeling inspired to support Swallowtails in your own space?

Here are some California native larval host plants and nectar plants available now!

Larval Host Plants (what the caterpillars eat):

California Dutchman’s Pipe

Aristolochia californica

Available in D-16 pots for $6.60 each!

A robust, perennial, deciduous vine which can serve as small-scale groundcover under oaks, coffeeberry, spicebush, or pink-flowering currant
Rope-like stems can reach up to 12 ft in length once established, and its heart-shaped leaves drape beautifully over a trellis or fence line. Prefers part-shade to shade, dry-moderate moisture, and can tolerate clay, loam and sandy soil.
Larval food source for the pipevine swallowtail butterfly, nectar source for carrion-feeding insects
Most notable for its odd, bulbous 1-½ inch tubular pipe-shaped flowers, (the
Dutchman’s pipe) which provide early nectar resources in winter and spring, dangling from bare stems

Coast Angelica

Angelica hendersonii

Available in D-40 pots for $8.80 each!

Like other parsley family members, this species is a larval host plant for Anise Swallowtail caterpillars!
A showstopper in bloom, this tall evergreen is adapted to a well-draining soil and coastal sage-scrub habitat, where it can grow to be over 4 ft tall when in bloom
Deep green, lobed basal leaves have white, wooly undersides
A wonderful addition to any pollinator garden, Coast Angelica blooms in late spring and summertime, with showy, broad, umbel-shaped white flowers that provide nectar and pollen to numerous pollinators

Oregon Ash

Fraxinus latifolia

Available in D-40 pots for $9.00 – $9.90 and TB4 pots for $13.00 – $14.30 each!

Larval host plant for the Western Tiger Swallowtail and Two-Tailed Swallowtail
Deciduous, medium sized tree (30 – 80 ft. tall)
Symmetrical in shape, half as wide as it is tall; space 30 ft. apart
fast growing for first 1/3 of life (can reach 250 years old!)
Common in riparian habitats, and looks best in moist sites but can grow in dry sites
Prefers full sun to part shade, poorly drained/moist land with deep soil rich in humus
Good for erosion control
Seeds provide valuable food for birds and squirrels

California Coffeeberry

Frangula californica

(formerly called Rhamnus californica)

Available in D40 pots for $9.90 each!

Larval host plant for Pale Swallowtail caterpillars
Nectar source for a variety of butterflies
Evergreen shrub, fast growing to 6 – 8 ft. tall
Named for the seeds contained in its berries which resemble coffee beans
Excellent foliage plant with showy red fruit, beautiful reddish branches, and deep green lustrous leaves
Well suited for informal hedges or screens; tolerant of pruning
Tiny flowers attract hummingbirds, native bees, and butterflies throughout spring
Drought tolerant and can grow in full sun to part shade in a variety of soil types

Nectar Plants (what the adult butterflies eat):

California Buckeye

Aesculus californica

Available in TB4 pots for $14.30 each!

Valuable nectar source for a variety of butterflies, bees, and hummingbirds thanks to its candelabra-like flowers that bloom from April – June
Drought tolerant, deciduous tree that can grow ~ 3 ft. per year up to 15 – 40 ft. tall, with a spread of 30 – 60 ft. (space 30 ft. apart)
Provides year-round beauty to the garden, even while dormant
Can grow in full sun to part shade with nearly any water and soil conditions.

Western Azalea

Rhododendron occidentale

Available in D40 pots for $9.90 each!

Valued nectar source for Pipevine Swallowtails and other butterfly species
Deciduous shrub reaching 2 – 5 ft. tall
Delicate white blooms tinged with pink, yellow, and orange have a sweet fragrance that is a delight in the garden
Can be slow growing, but worth the wait!
Prefers acidic soil, so best planted under redwoods or with added organic matter (peat moss or compost)

Yerba Santa

Eriodictyon californicum

Available in D40 pots for $7.43 – $9.90 each!

Blue – pink flowers that bloom in the spring are an excellent source of nectar for many butterfly species
Evergreen shrub that grows ~5 – 7 ft. tall x 4 ft. wide
Leaves are edible and can be made into tea
Very drought tolerant and grows well with Oaks, Mountain Mahogany, Ceanothus, and Manzanitas.
Can be grown to create a hedge

Silver Bush Lupine

Lupinus albifrons

Available in D40 pots for $9.90 each!

Large, fragrant, vibrant purple flowers bloom throughout spring and summer, providing fantastic nectar source for a wide variety of butterfly species and smell like grape soda 🙂
Host plant of the endangered Mission Blue Butterfly
Easy-to-grow perennial shrub, 3 – 5 ft. tall
Very drought tolerant, and a terrific choice rock garden, dry border, parking strip, or large container
Prefers full sun with well-drained soil
Named for its outstanding shimmering silvery green foliage that forms an attractive, dense mound

Coyote Mint

Monardella villosa

Available in D16 pots for $6.60 each!

Bright purple flowers provide valuable nectar for a bunch of different butterfly species while in bloom all summer from June – August
Perennial wildflower found only in California
Grows as a small, mat-forming shrub ~2 ft tall and wide
Leaves have a lovely minty scent that can be seeped to make tea
Plant in full sun to part shade with little water and well draining soil

Works Cited

“Anise Swallowtail, Papilio Zelicaon.” Calscape.org, calscape.org/lep/Papilio-zelicaon-(Anise-Swallowtail)?srchcr=sc64f0db0c2894c. Accessed 30 Aug. 2023.

“Anise Swallowtail Papilio Zelicaon Lucas, 1852 | Butterflies and Moths of North America.” Www.butterfliesandmoths.org, www.butterfliesandmoths.org/species/Papilio-zelicaon.

Buehler, Jake. “Butterflies May Lose Their “Tails” like Lizards.” Science News, 15 June 2022, www.sciencenews.org/article/butterfly-wing-tail-loss-break-birds-escape.

“Butterflies of California.” INaturalist, www.inaturalist.org/check_lists/10675-Butterflies-of-California. Accessed 30 Aug. 2023.

Chotard, Ariane, et al. “Evidence of Attack Deflection Suggests Adaptive Evolution of Wing Tails in Butterflies.” Proceedings of the Royal Society B: Biological Sciences, vol. 289, no. 1975, 25 May 2022, https://doi.org/10.1098/rspb.2022.0562. Accessed 31 Aug. 2023.

Kolehouse , Courtney. “Battus Philenor-Adaptation.” Bioweb.uwlax.edu, 26 Apr. 2014, bioweb.uwlax.edu/bio203/s2013/kolehous_cour/adaptation.htm.

Kristen. “Variations on a Theme: Chrysalis Colors.” MOSI Outside, 16 Oct. 2012, lepcurious.blogspot.com/2012/10/variations-on-theme-chrysalis-colors.html#:~:text=High%20levels%20of%20hormone%20will. Accessed 1 Sept. 2023.

Lees, David. “Do Butterflies Taste with Their Feet?” Www.youtube.com, Natural History Museum, London, 24 Apr. 2023, www.youtube.com/watch?v=VoVh2PbSAC4. Accessed 31 Aug. 2023.

Lees, David, and Alison Shean. “A Closer Look at Butterfly Senses.” Www.youtube.com, Natural History Museum, London, 27 Apr. 2023, www.youtube.com/watch?v=T7dnomHrUb4. Accessed 31 Aug. 2023.

Nagaya, Hiromi, et al. “Swallowtail Butterflies Use Multiple Visual Cues to Select Oviposition Sites.” Insects, vol. 12, no. 11, 22 Nov. 2021, p. 1047, www.ncbi.nlm.nih.gov/pmc/articles/PMC8622024/, https://doi.org/10.3390/insects12111047. Accessed 31 Aug. 2023.

“Pale Swallowtail Papilio Eurymedon Lucas, 1852 | Butterflies and Moths of North America.” Www.butterfliesandmoths.org, www.butterfliesandmoths.org/species/Papilio-eurymedon. Accessed 30 Aug. 2023.

“Pale Tiger Swallowtail, Papilio Eurymedon.” Calscape.org, calscape.org/lep/Papilio-eurymedon-(Pale-Tiger-Swallowtail)?srchcr=sc64f10557d3a4a. Accessed 30 Aug. 2023.

“Papilio Eurymedon.” Wikipedia, 31 Mar. 2022, en.wikipedia.org/wiki/Papilio_eurymedon#:~:text=Their%20appearance%20is%20quite%20similar. Accessed 30 Aug. 2023.

“Papilio Eurymedon | Art Shapiro’s Butterfly Site.” Butterfly.ucdavis.edu, butterfly.ucdavis.edu/butterfly/papilio/eurymedon. Accessed 31 Aug. 2023.

“Papilionidae.” Tolweb.org, tolweb.org/Papilionidae/12177. Accessed 31 Aug. 2023.

“Pipevine Swallowtail.” LIBRARIES of LIFE, www.libraries-of-life.org/pipevine-swallowtail.html. Accessed 30 Aug. 2023.

“Pipevine Swallowtail Battus Philenor (Linnaeus, 1771) | Butterflies and Moths of North America.” Www.butterfliesandmoths.org, www.butterfliesandmoths.org/species/Battus-philenor.

Rourke, Kelly. “Pipevine Swallowtail.” Www.fs.usda.gov, United States Department of Agriculture, www.fs.usda.gov/wildflowers/pollinators/pollinator-of-the-month/pipevine-swallowtail.shtml.

Shapiro, Art. “Battus Philenor | Art Shapiro’s Butterfly Site.” Butterfly.ucdavis.edu, butterfly.ucdavis.edu/butterfly/battus/philenor. Accessed 31 Aug. 2023.

“Western Tiger Swallowtail, Papilio Rutulus.” Calscape.org, calscape.org/lep/Papilio-rutulus-(Western-Tiger-Swallowtail)?srchcr=sc64f10557d3a4a. Accessed 31 Aug. 2023.

“Western Tiger Swallowtail Papilio Rutulus Lucas, 1852 Butterflies and Moths of North America.” Www.butterfliesandmoths.org, www.butterfliesandmoths.org/species/Papilio-rutulus.

“What Are Swallowtails and Birdwings?” Swallowtail and Birdwing Butterfly Trust, 8 Aug. 2017, www.sbbt.org.uk/what-are-swallowtails-birdwings/biology/. Accessed 31 Aug. 2023.

“Why Butterflies Are Beneficial to the Environment.” Good Living, 9 Feb. 2022, www.environment.sa.gov.au/goodliving/posts/2018/12/benefits-of-butterflies#:~:text=They. Accessed 31 Aug. 2023.

Stay Safe, ‘Bee’ Well, and Go Natives!

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