Butterflies of America: Native Species and Regions

The United States is home to approximately 750 recorded butterfly species. These insects act as pollinators and indicators of environmental health, and understanding their diversity offers a window into the natural world.

Prominent American Butterfly Families and Species

The butterflies of the United States are categorized into several families. The Papilionidae family, or swallowtails, includes some of the largest butterflies in North America, distinguished by colorful patterns and tail-like extensions on their hindwings. A common example is the Eastern Tiger Swallowtail.

The Nymphalidae family, or brush-footed butterflies, includes monarchs, fritillaries, and the Mourning Cloak. Their name comes from reduced front legs not used for walking. Fritillaries have silver spots under their wings, while the Mourning Cloak can overwinter as an adult.

The Pieridae family consists of the whites and sulphurs. The Cabbage White, an introduced species, is one of the most widespread butterflies in North America. Cloudless Sulphurs are known for their yellow wings and migratory behavior.

Lycaenidae is a family of smaller butterflies including blues, coppers, and hairstreaks, which are named for the hair-like tails on their hindwings. The Western Pygmy-Blue is the smallest butterfly in North America.

The Hesperiidae family, or skippers, are known for quick, erratic flight. They are distinguished by features like hooked antennae and robust, moth-like bodies.

Regional Butterfly Diversity Across the US

Butterfly distribution varies across the United States, as each region’s climate and ecosystem supports different species. The Northeast’s forests and meadows are home to species like the Spring Azure and Harris’ Checkerspot, with populations shifting with the seasons.

The warm, humid Southeast supports a high diversity of butterflies, including the Gulf Fritillary and Zebra Swallowtail. The region’s long growing season allows for multiple generations of many species a year. Southern Florida’s subtropical environment hosts unique tropical species.

The Midwest’s prairies are home to grassland specialists like the Regal Fritillary and Ottoe Skipper, whose survival depends on remaining patches of native prairie. The more arid Great Plains supports butterflies adapted to open, windswept environments.

The Rocky Mountains host unique butterfly fauna in their varied elevations and alpine meadows. Species like the Melissa Arctic and the Phoebus Parnassian are adapted to high-altitude conditions, and changes in elevation create microclimates that support different butterfly communities.

The Southwest’s contrasting deserts and mountains result in a high number of butterfly species, such as the Queen and the Pipevine Swallowtail. Its ‘sky island’ mountain ranges create isolated habitats for unique subspecies.

The Pacific Northwest’s moist forests and coastal areas support species like the Lorquin’s Admiral and the Pale Swallowtail. California has a high level of biodiversity due to its many distinct ecosystems.

American Butterfly Life Cycles and Native Host Plants

A butterfly’s life cycle unfolds in four distinct stages: egg, larva, pupa, and adult. Adult butterflies lay their eggs on or near specific host plants that will serve as food for their offspring. The selection of the right host plant is necessary, as the emerging larva, or caterpillar, depends on a specific plant species or family for food.

Once hatched, the caterpillar’s primary function is to eat and grow, shedding its skin multiple times. Caterpillars of the Black Swallowtail, for example, feed on plants in the carrot family like parsley and dill. Some caterpillars store toxins from host plants, making them and the resulting adult butterfly unpalatable to predators.

After reaching its full size, the caterpillar transforms into a pupa, or chrysalis. During this non-feeding, immobile stage, the caterpillar’s body reorganizes into its butterfly form, a transformation that can take weeks or months. The Monarch chrysalis, for instance, is jade green with gold markings.

The final stage is the emergence of the adult butterfly, whose soft, folded wings are pumped with fluid to expand and harden. The butterfly then takes flight to feed on nectar, mate, and lay eggs. While caterpillars need specific host plants, adults visit a wider variety of flowers for nectar.

Remarkable Butterfly Migrations in America

The multi-generational migration of the Monarch butterfly spans thousands of miles from Canada and the United States to overwintering sites in central Mexico. The migration is a relay involving several generations, so no single butterfly completes the round trip. The generation that flies south to Mexico lives for many months to survive the winter.

These Monarchs are in a state of reproductive diapause, not mating or laying eggs until the following spring. They use environmental cues like the sun’s angle and the earth’s magnetic field to navigate to ancestral overwintering sites. They cluster in oyamel fir forests, covering trees in a blanket of orange and black.

While the Monarch’s migration is famous, other North American butterflies also undertake long-distance movements. The Painted Lady is known for massive, irregular migrations tied to weather patterns and the availability of its thistle host plants. These movements are not a predictable annual event like the Monarch’s.

Other migratory species include the Cloudless Sulphur, Red Admiral, and Common Buckeye. These butterflies move northward in the spring and summer, with subsequent generations continuing the journey. For most of these species, the migration is a one-way trip for the individuals involved.

Conserving and Attracting Butterflies in the United States

Butterfly populations in the United States face several threats that have led to declines in many species. Habitat loss from urban development and agriculture is a primary pressure, removing the host plants and nectar sources butterflies need. The widespread use of pesticides is also harmful, as insecticides can kill butterflies directly, while herbicides eliminate native plants.

Climate change presents another challenge, as it can alter the timing of flower blooming and butterfly emergence, creating a mismatch with their food sources. Conservation efforts are underway to protect and restore butterfly habitats. These initiatives involve planting native species, managing landscapes for biodiversity, and reducing pesticide use.

Citizen science programs, such as the Butterflies and Moths of North America (BAMONA) project, allow the public to contribute to research by submitting observations. Individuals can support local butterfly populations by creating butterfly-friendly gardens.

This involves planting native host plants for caterpillars and a variety of nectar-rich flowers that bloom throughout the season. Providing a shallow water source and avoiding the use of pesticides also makes a garden more welcoming for butterflies.