Butterflies of Pennsylvania

By Karin Bolcshazy

A total of 146 species of butterflies have been reported in Pennsylvania, according to Penn State Extension. About 24 have been documented only a few times in the state and might best be considered rare visitors.

Butterflies range from the various, small, brown skipper species with wingspans as small as a halfinch to the tiger swallowtail, which can have a wingspan of about 5.5 inches. Some are so tightly connected to specific habitats or plants that most people will never see them.

Here are some facts about the more easily observed ones:


The Viceroy mimics the coloring of the monarch and gains some protection from predators because of the foul taste and toxic qualities of those it mimics. The caterpillar of the viceroy is a master of camouflage, looking exactly like a bird dropping.

Wingspan: 2.5-3 inches.

Caterpillar host plants: Willows, poplars, aspens and fruit trees.

Adult nectar sources: Wide variety of wildflowers and tree blossoms.


The Spring Azure is among the first butterflies of the year. The upper side of males is iridescent blue, while the upper side of females is blue with a dark border. The underside is pale gray to whitish, with small dark spots. Larvae are variable, downy green to yellowish green to reddish brown, with a darker stripe along the back and oblique (slanting) greenish side lines. The head is brown with black edging. Spring and 'Summer' Azures inhabit woodland edges and openings, and readily visit garden flowers. 'Atlantic' Azure is found in forested areas, often near bogs and cedar swamps.

Wingspan: 1 inch

Caterpillar host plants: flowers and fruits of a variety of woody and nonwoody plants, including flowering dogwood, New Jersey tea, blue-eyed Mary, and many more.

Adult nectar sources: flowering plants, including wild plum, early-blooming milkweeds and dogbanes, New Jersey tea, blackberries and their relatives, and other springtime flowers


The Zebra Swallowtail is native to the eastern United States and southeast Canada. Its distinctive wing shape and long tails make it easy to identify, and its black and white-striped pattern is reminiscent of a zebra. The butterflies are closely associated with pawpaws, and are rarely found far from these trees. The triangular wings are white to greenish-white with black longitudinal stripes. A pair of swordlike tails extend from the hind wings. The inner margin of the hind wing has two blue spots on the corner and a red spot near the body. A red stripe runs along the middle of the ventral hind wing. The zebra swallowtail prefers corridors of wooded land alongside bodies of water such as riversides, lakeshores, marshes and open moist woods.

Caterpillars are generally hairless. They have a forked gland called the osmeterium that can protrude from the back of the head if the butterfly is alarmed and releases a bad smell that is used as defense mechanism.

Wingspan of 2-3 inches

Caterpillar host plants: feeds only on species within the genus Asimina (PawPaw). P. marcellus caterpillars ingest chemicals called annonaceous acetogenins from their host plants, which are retained in the body tissues of both the caterpillar and the adult, and may help chemically protect the butterfly from birds.

Adult nectar sources: Pawpaw; favorite nectar plants are Milkweed, Cosmos, Sweet William, and Zinnia.


One of the first butterflies to be spotted in the spring, Male Mourning Cloaks perch in sunny openings in the forest in the afternoon to wait for females ready for breeding. Eggs will hatch, and caterpillars will live in a communal web until June or July, when they will pupate and emerge as adults. Those adults will feed briefly then estivate until fall, when they emerge again, feed and enter hibernation until next spring. The adult's dusky wings are edged with a cream-colored border, which is followed by a narrow black strip bearing a path of small azure spots.

Wingspan: 2.25-4 inches.

Caterpillar host plants: Deciduous trees and shrubs, particularly willow poplar and ash.

Adult nectar sources: Rotting fruit, butterfly bush, milkweed, New Jersey tea, Shasta daisy, doghouse and pussy willow.


The Silver-Spotted Skipper is one of the most common and widespread butterflies across North America. It is mostly a mottled brown color, but when its wings are raised up, a large white-silver patch can easily be seen on the lower hindwings. It can take advantage of a wide range of habitats, both manmade and natural.

Wingspan: 1.75-2.5 inches.

Caterpillar host plants: Wisteria, licorice, beans and locusts.

Adult nectar sources: Many species of wild and domestic flowers. Credits: pennlive.com; Missouri Dept. of Conservation; inaturalist.org