Swallowtail butterflies are known for their striking colors and large size, making them a delight for anyone to observe. Among these captivating creatures, two notable species are the Eastern Giant Swallowtail (Papilio cresphontes) and the Western Giant Swallowtail (Papilio oregonius).
The Eastern Giant Swallowtail can be found throughout the eastern United States and even in parts of Mexico, while the Western Giant Swallowtail, also known as the Oregon Swallowtail, is primarily found in the Northwestern United States. Both species display stunning color patterns on their wings, showcasing a combination of black, yellow, red, and blue.
Despite their similarities, subtle differences exist between the Eastern and the Western Giant Swallowtail. For instance, the yellow wing markings of the Oregon Swallowtail are brighter than the Eastern counterpart, setting them apart visually. Additionally, their habitats and preferred host plants for their caterpillars may vary, with the Eastern species being more prevalent in regions with citrus trees. Comparing these captivating species can provide a deeper understanding and appreciation for the world of Swallowtail butterflies.
Eastern and Western Giant Swallowtail Butterflies
Scientific Classification
Eastern Giant Swallowtail (Papilio cresphontes) and Western Tiger Swallowtail (Papilio rutulus) butterflies belong to the order Lepidoptera and family Papilionidae. Here’s a brief comparison of their classification:
| Butterfly | Genus | Species | Synonyms |
|---|---|---|---|
| Eastern Giant Swallowtail | Papilio | cresphontes | Papilio cresphontes Cramer |
| Western Tiger Swallowtail | Papilio | rutulus |
Physical Characteristics
Giant Swallowtail and Western Tiger Swallowtail butterflies possess notable physical features:
- Eastern Giant Swallowtail: Black wings with yellow bands forming an “X” shape across the wingspan. Full wingspans range from 100 to 160 mm. Female butterflies typically larger with bluer hindwings.
- Western Tiger Swallowtail: Yellow wings with black stripes, resembling tiger fur pattern. Wingspans range from 70 to 100 mm.
Lifecycle
Eastern Giant Swallowtail
- Females lay eggs on citrus trees, prickly ash, and common rue.
- Eggs hatch in about 10 days.
- Caterpillars last around 3-4 weeks.
- Adult lifespan: 1-2 weeks.
Western Tiger Swallowtail
- Females lay eggs on tree leaves.
- Eggs hatch in about a week.
- Caterpillars last around 4-6 weeks.
- Adult lifespan: about 3 weeks.
Habitat
Giant Swallowtail and Western Tiger Swallowtail butterflies prefer differing habitats:
- Eastern Giant Swallowtails: Commonly found in citrus groves, gardens, and woodland edges in the southeastern United States.
- Western Tiger Swallowtails: Generally inhabit riparian zones, woodlands, and gardens throughout the western United States.
Distribution and Range
Eastern Giant Swallowtail
The Eastern Giant Swallowtail has a wider range, predominantly found in the eastern regions of North America. Key areas include:
- United States: East of the Mississippi River and extending into the Great Plains states1
- Mexico: Several states1
- Jamaica and Cuba2
They are largely found in deciduous forests and wooded areas.
Western Giant Swallowtail
In comparison, the Western Giant Swallowtail has a more limited distribution, primarily in specific regions:
Their habitats usually include woods and areas with citrus host plants.
Comparison Table
| Eastern Giant Swallowtail | Western Giant Swallowtail | |
|---|---|---|
| Range | Eastern North America | Florida, Arizona, Southern Mexico |
| United States | East of Mississippi River, Great Plains states | Florida, Arizona |
| Mexico | Several states | Southern areas |
| Habitat | Deciduous forests, wooded areas | Woods, citrus host plants areas |
Host Plants and Nectar Sources
Citrus
The giant swallowtail butterfly, specifically the Eastern and Western species, belong to the family Papilionidae and are commonly found in citrus orchards. Their host plants mainly come from the Rutaceae family, such as sweet orange (citrus × sinensis), lime, and other citrus plants. These plants serve as a vital food source for the larvae, also known as orange puppies1. Here are some common citrus host plants:
- Sweet Orange (Citrus × sinensis)
- Lime
- Hoptree (Ptelea trifoliata)
In addition to these host plants, nectar plants like Lantana, Bougainvilla, and Lonicera japonica attract both species of giant swallowtails by providing nectar as an adult food source2.
Non-Citrus
Giant swallowtails can also utilize non-citrus host plants, particularly species within the Zanthoxylum genus such as3:
- Gasplant (Zanthoxylum fagara)
- Hercules club (Zanthoxylum clava-herculis)
- Prickly Ash (Zanthoxylum americanum Mill)
- Lime pricklyash (Zanthoxylum clava-herculis)
These plants, while not citrus, still belong to the Rutaceae family and serve as essential host plants for both Eastern and Western giant swallowtails. Nectar sources for non-citrus host plants also include Solidago (goldenrods), Milkweed, and Amyris elemifera4.
Comparison Table
| Features | Citrus | Non-Citrus |
|---|---|---|
| Host Plants | Sweet Orange, Lime, Hoptree | Gasplant, Hercules club, Prickly Ash, Lime pricklyash |
| Nectar Sources | Lantana, Bougainvilla, Lonicera japonica | Solidago, Milkweed, Amyris elemifera |
In summary, both Eastern and Western giant swallowtails have evolved to utilize a variety of host plants and nectar sources, mainly within the Rutaceae family. While citrus plants are essential hosts for these butterflies, they also thrive on non-citrus plants, allowing them to adapt and survive in various environments5.
Development and Adaptations
Larval Instars and Chrysalis
Eastern and Western Giant Swallowtails go through five larval instars before transforming into a chrysalis. Key differences include:
- Eastern Giant Swallowtail:
- Larger in size
- Chrysalis color: green or brown, resembling a twig
- Western Giant Swallowtail:
- Smaller in size
- Chrysalis color: mainly brown, resembling dry leaves
Caterpillar and Bird Droppings Mimicry
Both Eastern and Western Giant Swallowtails show amazing adaptations for survival. Young caterpillars resemble bird droppings, which helps in deceiving predators. As they mature, coloration and shape changes along with their instars.
Osmeterium and Setae
Apart from visual mimicry, caterpillars have an osmeterium, a fleshy appendage that emits a foul-smelling substance when threatened. This helps deter predators from eating them.
| Eastern Giant Swallowtail | Western Giant Swallowtail | |
|---|---|---|
| Osmeterium | Available | Available |
| Setae (bristles) | Sparse bristles | Denser bristles |
In summary, Eastern and Western Giant Swallowtails show remarkable adaptations for survival, including bird droppings mimicry and the use of osmeterium and setae to deter predators. Their larvae undergo five instars before forming chrysalis, with differences in size, coloration, and bristle density.
Natural Enemies and Pests
Vertebrate Predators
Giant swallowtail butterflies, both eastern and western, face challenges from several vertebrate predators. Some common predators include:
- Birds, which feed on caterpillars and adult swallowtail butterflies
- Lizards and small mammals that prey on caterpillars
Unfortunately, these predators can be challenging for entrepreneurs involved in butterfly farming or conservation efforts, as they reduce the number of healthy, viable butterflies.
Parasitoids
Parasitoids are organisms that ultimately lead to the death of their host. In the case of giant swallowtails, these can include several species of wasps:
- Brachymeria robusta
- Pteromalus cassotis
- Pteromalus vanessae
- Lespesia rileyi
The wasps lay their eggs in swallowtail caterpillars, and the wasp larvae eventually kill their host, causing damage to the butterfly population.
Comparison Table
| Species | Host | Type |
|---|---|---|
| Brachymeria robusta | Giant Swallowtails | Parasitic Wasp |
| Pteromalus cassotis | Giant Swallowtails | Parasitic Wasp |
| Pteromalus vanessae | Giant Swallowtails | Parasitic Wasp |
| Lespesia rileyi | Giant Swallowtails | Parasitic Wasp |
Pests
Giant swallowtails are also affected by common pests, such as mites and aphids, which can cause damage to their food sources. Caterpillar’s primary food plants include the leaves of various citrus trees.
Key Characteristics of Giant Swallowtails’ Pests:
- Mites: microscopic arachnids that cause damage to the leaves
- Aphids: small insects that feed on plant sap and weaken the plant
Prehistoric vertebrates are not directly affecting the current population of giant swallowtails, but their evolutionary past might have played a role in shaping their defenses against natural enemies and pests today.
Interaction with Humans
Citrus Industry and Pest Management
The Eastern and Western Giant Swallowtails, members of the Papilionidae family, have a significant impact on the citrus industry. Their caterpillars, known as Orange Dog, feed on citrus leaves, causing damage to citrus farms. Some key differences between the two species include:
| Eastern Giant Swallowtail | Western Giant Swallowtail |
|---|---|
| Found in the eastern US | Found in the western US |
| Prefers nectar sources like milkweed and wild cherry | Prefers nectar sources like fennel and lantana |
Pest Management
- Biological Control: Natural enemies, such as wasps and flies, help control the population of caterpillars.
- Cultural practices: Removing host plants reduces the appeal of citrus farms to the swallowtail species.
- Chemical control: Pesticides can be judiciously used to protect the citrus plants.
Bug Control Recommendation Tool
Conservation and Entomology
Both Eastern and Western Giant Swallowtails are essential in the field of entomology, as they are indicators of environmental health. Studying these butterflies helps scientists to understand factors that affect their populations, such as climate change and habitat fragmentation. Some measures to protect and conserve the Giant Swallowtails are:
- Creating butterfly gardens with preferred host and nectar plants for the respective species
- Avoiding the use of pesticides in home gardens, promoting a more butterfly-friendly environment
- Supporting research and conservation efforts by reporting swallowtail sightings to local naturalist groups
Species Comparison
Similar Swallowtail Species
Several swallowtail species share similar features with the Eastern Giant Swallowtail (Papilio cresphontes) and Western Giant Swallowtail (Papilio rumiko). Some of these species include:
- Polydamus Swallowtail
- Black Swallowtail
- Spicebush Swallowtail
- Pipevine Swallowtail
- Anise Swallowtail
- Zebra Swallowtail
- Two-Tailed Swallowtail
- Palamedes Swallowtail
These species are often found in similar habitats and sometimes have overlapping ranges.
Differences Between Eastern and Western Giant Swallowtails
While the Eastern and Western Giant Swallowtails are both large and vibrant species, they have some differences in appearance and behavior.
Appearance:
- Eastern Giant Swallowtails have a wider wingspan, reaching up to 6 inches, while Western Giant Swallowtails have a slightly smaller wingspan, usually around 5 inches.
- Female Black Swallowtails, closely related to the Eastern Giant Swallowtail, have larger hind wings with more blue pigmentation compared to their male counterparts.
- The Western Giant Swallowtail has a lighter yellow coloration on its wings than the Eastern Giant Swallowtail, which has a deeper, more saturated yellow color.
Behavior:
- Eastern Giant Swallowtails prefer to lay their eggs on plants from the citrus and rutaceae families, such as Ptelea trifoliata, while Western Giant Swallowtails are less specific and lay eggs on different host plants, including some non-native species.
| Aspect | Eastern Giant Swallowtail | Western Giant Swallowtail |
|---|---|---|
| Wingspan | Up to 6 inches | Around 5 inches |
| Wing Color | Deeper yellow | Lighter yellow |
| Preferred Host Plants | Citrus and rutaceae | Various |
By understanding the differences and similarities between the Eastern and Western Giant Swallowtails, one can better appreciate and identify these distinct and beautiful species.
Footnotes
our help!
Nancy Rennie
5 Comments.
I’m so glad I submitted this for you, and that you posted it. Thank you, and I’m glad you liked it! 🙂
It always pays to have a cell phone with a camera!! Hahaha
We spotted a mating pair in our garden, today. Southern California, near the Mexican border. Lovely to see!!
We wish you had a photo to submit.
This is a female GIant Swallowtail – Papilio cresphontes. It definitely is not Papilio thoas (which would be very unlikely in Arizona). The two are similar, but the patterns are different, and with practice they are not difficult to tell apart.
Thanks for providing information on this very old posting.