The pipevine swallowtail (Battus philenor) is a striking North American butterfly recognized by its black wings, shimmering blue or blue-green hindwings, and bright orange spots underneath. Its caterpillar is equally distinctive, with a dark body, orange tubercles, and long fleshy projections. Pipevine swallowtails depend on Aristolochia, or pipevine, plants during the larval stage. By storing defensive chemicals from these plants, the butterfly becomes distasteful to many predators, and several other butterflies have evolved to imitate its appearance.
What Is a Pipevine Swallowtail?
The pipevine swallowtail is a member of the swallowtail family Papilionidae. Its scientific name is Battus philenor, and it is also sometimes called the blue swallowtail.
The species occurs across much of the United States, with its distribution closely connected to the presence of suitable pipevine host plants.
Pipevine Swallowtail Quick Facts
- Scientific name: Battus philenor
- Family: Papilionidae
- Wingspan: About 2¾–5 inches
- Main color: Black with iridescent blue or blue-green
- Caterpillar color: Dark brown to black, sometimes reddish
- Host plants: Aristolochia species
- Adult food: Flower nectar
- Egg color: Reddish orange
- Chrysalis: Green or brown
- Special defense: Stores aristolochic acids from host plants
- Overwintering stage: Usually chrysalis in colder areas
Adults have a wingspan of roughly 72–132 mm, although size varies by region.
Pipevine Swallowtail Identification
From above, this butterfly is mainly black, but fresh adults can display beautiful metallic blue or blue-green across the hindwings.
The underside is particularly useful for identification because both sexes have a row of seven bright orange spots against an iridescent blue area on each hindwing.
Male Pipevine Swallowtail
Males generally show:
- Strong blue or blue-green iridescence
- Dark black forewings
- Small pale marginal spots
- Short swallowtail projections
- Seven orange spots underneath each hindwing
The iridescent coloration can appear dramatically different depending on sunlight and viewing angle.
Female Pipevine Swallowtail
Females have the same basic pattern but usually show duller blue iridescence on the upper hindwings.
Their pale marginal spots may also appear more conspicuous.
The underside of both males and females is quite similar, with the characteristic orange-spotted pattern.
Pipevine Swallowtail Caterpillar
The caterpillar is one of the easiest swallowtail larvae to recognize.
Fully grown larvae reach approximately 2 inches long. Most are dark brown or nearly black with rows of orange or reddish-orange bumps. Several fleshy projections extend from the body, with especially long filaments close to the head.
Caterpillar Identification
Look for:
- Dark brown or black body
- Velvety appearance
- Bright orange tubercles
- Long fleshy projections
- Two especially long projections near the front
- Approximately 2-inch mature length
Young caterpillars may feed together in groups, while larger larvae tend to become more solitary.
Why Are Some Caterpillars Red?
Pipevine swallowtail caterpillars are not always black.
A reddish form occurs, particularly in hot environments. Research summarized by the University of Florida notes that the red form predominates in parts of western Texas and southern Arizona when temperatures are relatively high.
Therefore, a red or orange-black caterpillar can still be Battus philenor.
What Do Pipevine Swallowtail Caterpillars Eat?
Pipevine swallowtail caterpillars specialize on plants in the genus Aristolochia, commonly called pipevines, Dutchman’s pipes, or birthworts.
They should not be expected to thrive on unrelated plants.
Important Host Plants
Host species include:
- California pipevine (Aristolochia californica)
- Virginia snakeroot (Aristolochia serpentaria)
- Woolly pipevine (Aristolochia tomentosa)
- Dutchman’s pipe (Aristolochia macrophylla)
- Other suitable regional Aristolochia species
Pipevine can lose substantial foliage when many caterpillars feed on it, but healthy established vines can recover.
Be Careful With Exotic Pipevines
Not every ornamental Aristolochia is a safe substitute.
For example, UF/IFAS warns that elegant Dutchman’s pipe or calico flower, Aristolochia elegans (also known as A. littoralis), can attract females to lay eggs even though pipevine swallowtail larvae often fail to survive on it.
For butterfly gardens, locally appropriate native host plants are usually the better choice.
Are Pipevine Swallowtail Caterpillars Poisonous?
Pipevine plants contain compounds called aristolochic acids. Caterpillars can sequester these chemicals while feeding and retain them through the pupal and adult stages.
These compounds make the butterflies distasteful or chemically defended against some predators. Even the next generation’s eggs can receive defensive compounds from females.
Are They Poisonous to Touch?
Pipevine swallowtail caterpillars are not considered stinging caterpillars.
Their long projections may look dangerous, but they are soft rather than venomous stingers.
Normal brief contact is not the same as ingesting the caterpillar or its host plant. Because the insects and pipevines contain biologically active compounds, however, unnecessary handling should be avoided, and children or pets should not be allowed to eat them.
Pipevine Swallowtail Eggs
Female pipevine swallowtails lay distinctive reddish-orange eggs on suitable pipevine plants.
The eggs may occur in groups, often on young plant growth or the underside of leaves.
What Do the Eggs Look Like?
They are:
- Reddish orange
- Rounded
- Small
- Often laid in clusters
- Covered partly with a nutrient-rich secretion
After hatching, young caterpillars commonly remain together and begin feeding on tender host foliage.
Pipevine Swallowtail Life Cycle
Like other butterflies, Battus philenor undergoes complete metamorphosis through four major stages: egg, larva, pupa, and adult.
In warm southern regions, several generations may develop during a single year. Farther north, fewer generations are typical.
Egg to Caterpillar
Females select suitable pipevine plants and deposit reddish-orange eggs.
After hatching, the larvae begin feeding on young leaves. Small caterpillars may remain together before dispersing as they grow.
Caterpillar to Chrysalis
A mature caterpillar eventually leaves its feeding site and finds a protected surface for pupation.
The caterpillar attaches itself with silk and transforms into a chrysalis.
Adult Butterfly
When development is complete, the adult emerges. Its wings initially appear soft and folded but gradually expand and harden.
In colder regions, the chrysalis is also the stage in which the butterfly commonly survives winter.
Pipevine Swallowtail Chrysalis
The pipevine swallowtail forms a chrysalis, not a true silk cocoon.
The two terms are often used interchangeably online, but butterflies generally form exposed pupae, while many moths surround their pupae with cocoons.
What Does the Chrysalis Look Like?
Pipevine swallowtail pupae can be:
- Green
- Brown
- Irregularly sculpted
- Angular
- Camouflaged against vegetation or bark
- Attached upright with silk
A distinctive feature is the widened, flange-like shape along the sides.
Brown coloration tends to be common, although the pupal environment can influence whether a chrysalis develops a greener or browner appearance.
Where Do Pipevine Swallowtails Live?
In the United States, the species occurs broadly from the eastern states westward through Texas and Arizona, along with an isolated population in northern and central California. Its broader range extends southward into Mexico.
California Pipevine Swallowtail
California’s isolated population is commonly referred to as the California pipevine swallowtail, Battus philenor hirsuta.
These butterflies are generally smaller and hairier than eastern populations. Their primary larval host is the native California pipevine, Aristolochia californica.
They are especially associated with stream corridors, foothill canyons, woodland, chaparral, and other places where California pipevine grows.
Pipevine Swallowtails in Texas and Florida
Texas supports pipevine swallowtails as well as the red larval form in especially hot western areas.
The butterfly also occurs in Florida, although its distribution there is stronger in central and northern portions than in the far south. Warm regions can support three or more generations during favorable years.
What Do Adult Pipevine Swallowtails Eat?
Adult butterflies drink flower nectar rather than eating pipevine leaves.
Useful nectar flowers include:
- Thistles
- Phlox
- Verbena
- Lantana
- Lupines
- Bergamot
- Azaleas
- Lilacs
- Teasel
- Other nectar-rich native flowers
Males also visit moist soil to obtain sodium and other minerals, a behavior called mud-puddling.
A good butterfly garden therefore needs both host plants for caterpillars and nectar plants for adults.
Pipevine Swallowtail vs. Black Swallowtail
The black swallowtail (Papilio polyxenes) can resemble the pipevine swallowtail, especially females.
However, the two differ noticeably.
Pipevine Swallowtail
- Strong blue hindwings
- Seven orange spots underneath
- Caterpillars feed on pipevine
- Chemically defended
Black Swallowtail
- More yellow spotting
- Different underside pattern
- Caterpillars commonly feed on parsley-family plants
- Adults imitate the pipevine swallowtail’s warning appearance
In fact, the pipevine swallowtail acts as a defensive model that several other dark butterflies mimic.
Pipevine vs. Spicebush Swallowtail
The spicebush swallowtail is another dark butterfly that resembles Battus philenor.
Spicebush swallowtails usually have a different hindwing spot arrangement and their caterpillars feed on spicebush and sassafras rather than pipevine.
Like the black swallowtail, the spicebush swallowtail benefits from resembling the chemically defended pipevine swallowtail.
FAQs
What is the scientific name of the pipevine swallowtail?
Its scientific name is Battus philenor. It belongs to the swallowtail butterfly family Papilionidae.
What do pipevine swallowtail caterpillars eat?
They feed primarily on Aristolochia species, including California pipevine, Virginia snakeroot, woolly pipevine, and Dutchman’s pipe.
Are pipevine swallowtail caterpillars poisonous to touch?
They do not have venomous stinging spines and are not considered dangerous to touch briefly. However, they store defensive chemicals from their host plants and should not be eaten or unnecessarily handled.
What does a pipevine swallowtail chrysalis look like?
The chrysalis can be green or brown and has an angular, sculpted appearance with distinctive side flanges. It is attached to a supporting surface with silk.
How can you tell a male from a female pipevine swallowtail?
Males generally have brighter, stronger blue or blue-green iridescence on their upper hindwings. Females have duller iridescence and often more noticeable pale spots.