The large black and yellow butterflies seen flying around gardens and fields in many parts of the world are known as swallowtail butterflies. Swallowtails are a group of butterflies in the family Papilionidae, named after their distinctive tail-like hindwings that resemble the forked tails of swallow birds. With over 550 species, swallowtails are some of the most familiar and best-loved butterflies. Their stunning wings come in an incredible array of colors and patterns, making swallowtails stand out as some of the most beautiful butterflies on Earth.
What do swallowtail butterflies look like?
The most recognizable feature of swallowtail butterflies is their wings. Swallowtails are large butterflies, with wingspans between 2-6 inches wide depending on the species. The upper wing surfaces are black or dark-colored, with striking yellow, blue, orange, red, or green markings. The lower wing surfaces are more subdued, helping provide camouflage when the wings are closed. Swallowtails have a distinctive ‘tail’ on each hindwing, which may be long and slender or shorter and more triangular, but always accentuates their elegant silhouette in flight. Their bodies are mostly black, with yellow or white markings on the thorax. The coloring serves as a warning to potential predators that swallowtails are distasteful.
Common swallowtail species
Some of the most widespread and familiar swallowtail butterflies include:
- Eastern tiger swallowtail – Common across eastern North America, the eastern tiger swallowtail is the state butterfly of 5 states. It is black with yellow stripes and ‘tails’.
- Western tiger swallowtail – Found in western North America, the western counterpart to the eastern tiger swallowtail. It is yellow with black tiger stripe patterns.
- Black swallowtail – Abundant across North America, this large mostly-black swallowtail has yellow spots and striking blue and orange spots on the hindwings.
- Giant swallowtail – The largest butterfly in North America, its wingspan can reach up to 6 inches. Mostly black with broad yellow bands and tails.
- Zebra swallowtail – Named for its green and white striped appearance, it is found in the southeastern United States and parts of Central America.
- Canadian tiger swallowtail – Occurring across Canada and the northern United States, it has black wings with yellow margins and markings.
- Old World swallowtail – One of the most widespread swallowtails, found throughout Europe, Asia, and Africa. Primarily black with bold yellow markings.
Habitats
Swallowtail butterflies live in a diverse range of open and wooded habitats, including:
- Fields – especially wildflower meadows
- Grasslands
- Gardens
- Deciduous forests
- Swamps
- Scrublands
- Suburban parks and yards
Anywhere that provides bright sunshine, shelter, and the host plants their caterpillars rely on can support swallowtail butterflies.
Life Cycle and Metamorphosis
Like all butterflies, swallowtails undergo a complete metamorphosis with four life stages: egg, caterpillar, pupa, and adult.
Eggs: Female swallowtails lay single eggs on the leaves and stems of host plants. The round eggs are small, usually less than 2mm wide. They vary in color between species from yellow to pale green.
Caterpillars: The caterpillars hatch from the eggs after 3-10 days. Swallowtail caterpillars grow up to 2 inches long and are plump with distinct segments. They come in a range of colors like green, black, or yellow, and many have false eye spots to deter predators. Their bodies are covered in spines and they munch voraciously on the host plant leaves.
Pupa: When fully grown, the caterpillar forms itself into a pupa by attaching itself with silk to a stem or branch and molting its skin. The pupa has a smooth, solid case around the developing butterfly inside. It is camouflaged to look like part of the plant, often resembling a rolled up leaf.
Adult butterfly: After a pupal stage of 1-2 weeks, the adult butterfly emerges. The swallowtail will pump fluid into its crumpled wings to extend them and wait for them to dry and harden before taking its first flight. Adult swallowtails live for an average of 2-6 weeks.
Diet
Swallowtail butterflies drink nectar from flowers as adults, but their caterpillars are specialist feeders, eating only the leaves of specific host plants. Common host plants utilized by swallowtails include:
- Parsley
- Fennel
- Dill
- Citrus trees
- Carrot family plants
- Rue
- Ash trees
- Tulip tree
- Hop tree
- Milkweed
The caterpillars sequester toxins from the host plants that make them distasteful to predators. The adult butterflies retain these toxins, advertising their foul taste with their conspicuous wing patterns.
Threats
Many swallowtail species are thriving butterflies, but some face threats to their habitats and survival, including:
- Pesticide use – chemicals can be toxic to swallowtails and their caterpillar host plants
- Urbanization and habitat loss – swallowtails need undisturbed open spaces
- Invasive species – can displace native host plants swallowtails rely on
- Climate change – may alter suitable range and distribution
Conserving habitats with diverse nectar flowers and host plants can help support healthy swallowtail populations. Avoiding pesticides and planting butterfly gardens can also aid swallowtails.
Swallowtail Mimicry
Some harmless species imitate the appearance of bad-tasting swallowtails to protect themselves, a form of mimicry. Examples include the pipevine swallowtail mimicked by the spicebush swallowtail, and the Battus philenor swallowtail mimicked by the blue-eyed grayling butterfly. By looking like a toxic swallowtail, mimics avoid predation while expending less energy on bright coloration.
Conclusion
With their large size, elegant wings, and stunning patterns, swallowtail butterflies are some of the showiest and most recognized butterflies worldwide. These beauties delight observers as they dance through the air, pausing to sip nectar from bright flowers. Providing the right habitat can allow us to enjoy seeing swallowtails glide through parks and gardens. With over 550 species, swallowtails display incredible diversity, from the giant swallowtail with a 6 inch wingspan to tiny muted swallowtails only an inch wide. Whatever their size and colors, swallowtails give us glimpses of natural wonder.
| Swallowtail Species | Range | Wingspan | Host Plants |
|---|---|---|---|
| Eastern Tiger Swallowtail | Eastern North America | 3.5 – 6.5 inches | Cherry, Ash, Tulip Trees |
| Western Tiger Swallowtail | Western North America | 3.5 – 5.5 inches | Cottonwood, Ash, Cherry Trees |
| Pale Swallowtail | Central to Eastern North America | 2.5 – 4 inches | Carrot, Parsley, Dill |
| Black Swallowtail | Throughout North America | 3.5 – 4.5 inches | Carrot, Parsley, Fennel |
| Giant Swallowtail | Southeastern United States | 4.5 – 6 inches | Citrus Trees, Hoptree |
