The Pipevine Swallowtail caterpillar (Battus philenor) is a distinctive butterfly larva found across much of North America. Mature caterpillars are usually dark brown or black with bright orange spots and fleshy projections, although red forms also occur. They feed almost exclusively on pipevines in the genus Aristolochia, absorbing plant chemicals that make them distasteful to many predators. Despite their alarming appearance, these caterpillars do not have venomous stinging spines. Their unusual coloration, specialized diet, chemical defenses, and dramatic transformation make them fascinating garden visitors.
What Does a Pipevine Swallowtail Caterpillar Look Like?
Pipevine Swallowtail caterpillars change noticeably as they grow. Newly hatched larvae are small and covered with short orange tubercles. Later stages develop longer fleshy projections and darker coloration. Mature caterpillars are especially recognizable by the combination of a dark body, bright orange markings, and long projections near the front of the body.
Pipevine Swallowtail Caterpillar Identification
- Scientific name: Battus philenor
- Usually dark brown to black when mature
- Rows of bright orange tubercles
- Several long fleshy projections
- Fine hairs that create a velvety appearance
- Bright yellow defensive osmeterium behind the head
- Mature length around 2 inches
- Red forms occur in some populations
Full-grown larvae average about 50 mm, or roughly 2 inches long.
Why Are Some Caterpillars Red or Orange?
Not every Pipevine Swallowtail caterpillar has the familiar nearly black body.
Some mature larvae become reddish or orange-red while retaining darker projections and markings. Temperature appears to influence this color variation. In western Texas and southern Arizona, red larvae become especially common during hotter conditions above approximately 30°C or 86°F. Red individuals have also been recorded in Florida.
What Do Pipevine Swallowtail Caterpillars Eat?
Pipevine Swallowtail caterpillars are highly specialized feeders. Their larvae use plants in the genus Aristolochia, commonly known as pipevines or Dutchman’s pipes. Reports of regular feeding on unrelated plants are considered unreliable. Young caterpillars may initially feed together, but older larvae become more solitary and may wander when they have consumed most of a host plant.
Important Host Plants
Common larval host plants include:
- California pipevine (Aristolochia californica)
- Virginia snakeroot (Aristolochia serpentaria)
- Woolly Dutchman’s pipe (Aristolochia tomentosa)
- Dutchman’s pipe (Aristolochia macrophylla)
- Texas Dutchman’s pipe (Aristolochia reticulata)
- Watson’s Dutchman’s pipe (Aristolochia watsonii)
Native Aristolochia species within the butterfly’s range are important resources for caterpillar development.
How Much Do They Eat?
Pipevine Swallowtail caterpillars can consume substantial amounts of foliage.
Large groups of young larvae may heavily defoliate a host vine. Once food becomes scarce, older caterpillars may leave and search for another pipevine.
Interestingly, newly hatched larvae often eat their own eggshells before beginning to feed on leaves. Caterpillars may also consume their shed skins after molting, allowing them to recover nutrients.
Are Pipevine Swallowtail Caterpillars Poisonous?
Pipevine Swallowtail caterpillars have chemical defenses, but describing them simply as “poisonous” can be misleading. They absorb aristolochic acids from their pipevine host plants and retain these chemicals in their bodies. The compounds can make the caterpillars unpalatable to some predators and continue into the chrysalis, adult butterfly, and even the next generation’s eggs.
Can They Sting Humans?
Pipevine Swallowtail caterpillars do not have the venomous stinging spines found on caterpillars such as saddlebacks or puss caterpillars.
Their long projections look intimidating but are not stingers.
Like other swallowtail caterpillars, they possess an osmeterium, a forked defensive organ behind the head. When disturbed, the caterpillar can extend this brightly colored structure and release an unpleasant-smelling secretion intended to discourage predators.
Is It Safe to Touch One?
Accidental contact generally does not produce the type of painful sting associated with venomous caterpillars.
However, unnecessary handling is best avoided. Pipevine caterpillars contain defensive plant compounds, and handling any unidentified caterpillar can lead to irritation or accidental injury to the insect.
Observing or moving one with a leaf is usually preferable to picking it up directly.
Pipevine Swallowtail Caterpillar Life Cycle
The caterpillar is only one stage of the Pipevine Swallowtail’s complete metamorphosis. Females place reddish-orange eggs on pipevine leaves. Young larvae feed socially before gradually separating. Once mature, caterpillars leave their host plants to find protected places for pupation. In colder climates, the species commonly survives winter in the chrysalis stage.
Four Life Stages
- Egg: Reddish-orange eggs are placed on pipevine.
- Caterpillar: Larvae feed and pass through several instars.
- Chrysalis: Mature caterpillars pupate away from the host plant.
- Adult butterfly: Adults emerge, feed on nectar, mate, and reproduce.
Multiple generations may occur where the warm season is long.
Pipevine Swallowtail Caterpillar Instars
The caterpillar changes after each molt.
First-instar larvae have short orange tubercles with individual hairs. Second instars develop longer projections, and later instars become progressively darker and more glossy.
By maturity, several projections have become elongated filaments, especially near the front of the body.
Pipevine Swallowtail Chrysalis
When fully grown, the caterpillar stops feeding and wanders away from its pipevine. It selects a firm surface such as a tree trunk or similar structure and attaches itself using silk. Like other swallowtails, it forms a silk pad and a supportive silk girdle around the middle of its body before changing into a chrysalis.
What Does the Chrysalis Look Like?
Pipevine Swallowtail chrysalises may be:
- Green
- Brown
- Irregularly shaped
- Wider along the sides
- Attached upright with a silk girdle
Brown chrysalises appear to be particularly common. The pupa may remain dormant through winter before producing an adult the following season.
California Pipevine Swallowtail Caterpillar
California populations depend particularly heavily on California pipevine, Aristolochia californica. This native vine grows in parts of northern and central California and provides the larval food necessary for local populations.
California Pipevine Swallowtails also show some physical differences from eastern populations.
California Caterpillars
California individuals tend to have shorter thoracic filaments than eastern caterpillars. The adults are also generally somewhat smaller and hairier.
UC Agriculture and Natural Resources identifies California pipevine as the caterpillar host plant and recommends it for gardens intended to support the butterfly.
Pipevine Swallowtail Caterpillars in Texas and Florida
The species has a broad distribution, but caterpillar appearance and host plants vary regionally. Texas populations use native pipevines including Texas Dutchman’s pipe, while Florida and southeastern populations can use species such as Virginia snakeroot. Warm climates can support extended seasonal activity compared with colder northern regions.
Texas Caterpillars
Texas is particularly interesting because hot conditions can produce conspicuous red larvae.
Western Texas populations may contain far more red caterpillars when temperatures exceed approximately 86°F. Texas Dutchman’s pipe is also a documented larval host.
Florida Caterpillars
Pipevine Swallowtails also occur in Florida, although their distribution depends partly on suitable pipevine host plants.
Virginia snakeroot occurs from central Florida northward and serves as a host plant. Red caterpillars can occasionally occur during very hot weather as well.
Predators and Defense
Pipevine Swallowtail caterpillars have several defenses, but they are not completely protected from predators. Their orange-and-black coloration acts as a warning signal, while chemicals obtained from pipevine make many individuals unpleasant to eat. The osmeterium provides another layer of defense when the caterpillar is physically threatened.
Known Predators and Parasitoids
Recorded natural enemies include:
- Birds
- Anole lizards
- Predatory insect larvae
- Tachinid flies
- Ichneumon wasps
- Chalcid wasps attacking pupae
Some predators still eat Pipevine Swallowtail caterpillars despite their chemical defenses.
How to Care for a Pipevine Swallowtail Caterpillar
Anyone temporarily raising these caterpillars should focus on providing the correct host plant rather than experimenting with substitute foods. They are specialists and should be supplied with fresh, pesticide-free Aristolochia foliage appropriate to their region.
Basic Care
- Provide fresh native pipevine leaves.
- Replace wilted foliage regularly.
- Keep the enclosure ventilated.
- Remove caterpillar waste frequently.
- Never use pesticide-treated leaves.
- Provide climbing surfaces for mature larvae.
- Give wandering caterpillars space to pupate.
Avoid feeding unrelated plants simply because a caterpillar happens to crawl across them; wandering mature larvae may travel over many non-host plants.
FAQs
1. What does a Pipevine Swallowtail caterpillar look like?
Mature caterpillars are generally dark brown or black with bright orange tubercles and long fleshy projections. Some become predominantly red.
2. What does a Pipevine Swallowtail caterpillar eat?
It feeds on pipevines in the genus Aristolochia, including California pipevine, Virginia snakeroot, and woolly Dutchman’s pipe.
3. Are Pipevine Swallowtail caterpillars poisonous?
They store aristolochic acids obtained from their host plants, making them chemically defended and often distasteful to predators. They are not venomous stinging caterpillars.
4. Do Pipevine Swallowtail caterpillars sting?
No. Their fleshy projections are not stingers. They defend themselves partly by extending a forked osmeterium that releases a repellent odor.
5. How big does a Pipevine Swallowtail caterpillar get?
A fully grown caterpillar reaches approximately 2 inches (50 mm) long before leaving its host plant to form a chrysalis.