Summer Butterfly Guide

Look for these twelve summer butterflies in the Philadelphia region.

Welcome to summer in the Philadelphia area! As the temperature and humidity soar, so do the butterflies!

This is our third published butterfly guide. (Make sure you check out the early spring and late spring guides if you haven’t already!) In each guide we have included photos of butterfly specimens in our insect research collection. The Academy’s entomology collection houses about 4 million insect specimens and over 50,000 moth and butterfly specimens collected in North America over the last 200+ years. The specimens are used to document and understand insects in ways we would not be able to do with only written notes and photographs. Within the millions of species of insects on this planet – there are 20,000 species of butterflies worldwide and 130 in the Philadelphia area – collecting physical specimens is crucial for recognizing species and conducting research.

In this guide we have included photos and size to help you recognize the butterflies in your garden or local park. We also include information on where you can see these species and what types of plants their caterpillars feed on (known as host plants) for those who want to proactively seek out butterflies. Since we are often asked where insects go in winter, when the world becomes cold and quieter, we also included information on how these butterflies overwinter. You will see that some overwinter as larva or in chrysalis form. Others completely avoid the cold of winter by flying south! Finally, we also included how many generations per year each butterfly cycles through and other notable facts about their morphology or behavior.

Enjoy! And once you read through the guide please let us know in the comments below which butterflies are your favorites and which you have seen or hope to see this year.

Dorsal side – top of the butterfly
Ventral side – bottom of the butterfly

1) Pipevine Swallowtail (Battus philenor)

Dorsal view of a male Pipevine Swallowtail
Ventral view of the male Pipevine Swallowtail

Size: Large, around the size of an Orange
Generations per year: Two to Three
Overwinter As: Chrysalis (Pupa)

Interesting Facts:
This species accumulates toxins from its larval hostplant that make the adult butterflies unpalatable to predators, and it advertises its toxicity by its bright coloration of the wings-black and blue dorsal side of the wings, with orange spots on the ventral side. This “warning coloration” to birds serves as an important “model” for a number of mimics in our area, including the dark form female of the Tiger Swallowtail, female Black Swallowtail, female Spicebush Swallowtail (all covered in the two earlier guides), and both sexes of the Red-Spotted Purple (covered in this guide). The writer Oscar Wilde said imitation is the sincerest form of flattery, but in science we call it Batesian mimicry!

The Pipevine Swallowtail was the study species used in pioneering research on simple learning in insects: Experiments on populations in Texas demonstrated that females are able to form search images and learn during their lifetime to recognize leaf shapes of different pipevine species to aid in finding their host plants.

What do I plant to encourage it? Pipevines (Aristolochia spp.)
Where can I see it? Gardens that plant pipevines, including Chanticleer Garden in Wayne, PA (in association with cultivated Asian Aristolochia spp.) and Morris Arboretum and Bartram’s Garden (in association with cultivated Aristolochia macrophylla and other ornamental Aristolochia vines) in Philadelphia.

The dorsal view of a Pipevine Swallowtail. Notice the characteristic reflective scales. (Photo courtesy of Jane Ruffin)
A Pipevine Swallowtail rests on a flower after emerging from its chrysalis. This butterfly was reared by Jason Weintraub. (Photographed by Isa S. Betancourt)

2) Red-spotted Purple (Limenitis arthemis astyanax)

Dorsal view of a Red-Spotted Purple that was collected in Tacony Creek Park on July 16th, 1965
Dorsal view of a Red-Spotted Purple
Ventral view of the Red-Spotted Purple

Size: Males are medium-small, around the size of a Lime. Females are medium sized, about the size of an orange.
Generations per year: Two
Overwinter As: Young larva

Interesting Facts:
This butterfly is a Batesian mimic of the Pipevine Swallowtail. Further north (in the Poconos), the subspecies Limenitis arthemis arthemis (“White Admiral”) occurs. These two subspecies inter-breed and one can find individuals with partial faint white wing bands that are in between the color patterns of the Red-spotted Purple phenotype (unbanded) and White Admiral phenotype (with broad white bands across wings). Only the asytanax subspecies is a mimic of the Pipevine Swallowtail.

The young larvae use silk to make a leaf shelter on their host plant in which they overwinter. Since their host plant’s leaves fall from the trees during autumn, they use silk to secure their leaf shelter to the tree. This overwintering shelter is called a hibernaculum.

Iridescent blue scales decorate the wings of the Red-spotted Purple butterfly. (Photo by Dr. Jon Gelhaus)

What do I plant to encourage it? Wild Cherry (Prunus serotina)
Where can I see it? Forests, open areas. Often seen on the ground or shrubs displaying, puddling or feeding on ripe fruit.

A Red-spotted Purple butterfly feeds on a fig fruit. (Video by Dr. Jon Gelhaus)

3) Red Admiral (Vanessa atalanta)

Dorsal view of the Red Admiral
The ventral view of the Red Admiral. With reared specimens in the collection, it is customary to include the pupal exuvia (or cast pupal exoskeleton) on the pin. You can even see the collector’s rearing notes among the labels: “Host: Urtica dioica / Emgd: vii.18.79”. The rearing notes tell us that this butterfly ate stinging nettle as a caterpillar (Urtica dioica) and emerged from its chrysalis on July 18th, 1979.

Size: Medium-small, around the size of a Lime
Generations per year: Two
Overwinter As: chrysalis (pupa); sometimes adults can survive the winter further south

Interesting Facts:
This species occurs throughout the Northern Hemisphere and is a common sight in temperate zone Europe (including Great Britain) as well as China and Japan.

Male Red Admirals are very territorial. They select a sunny patch of space and perch there during the afternoon to watch for passing females. They defend this space. They will harass other butterflies and other animals, including humans, by flying at them from their perch and shooing them away from the spot. If you think you’ve found a friendly red admiral butterfly because it has landed on you, think again! It is likely that it is a male that is trying to scare you away from his territory.

A Red Admiral rests on a sunny patch on the side of the trunk of a tree.
(Photo by Dr. Jon Gelhaus)
This Red Admiral was paying close attention to the presence of photographer as she entered his sunny territory one summer afternoon. Notice the characteristic red bands on the butterfly’s wings. (Photo by Isa S. Betancourt)
The red admiral will visit more than just flowers for nutrients. Here it is gathering nutrients from a fig. (Video by Dr. Jon Gelhaus)

What do I plant to encourage it? Nettles (Urtica spp.), False nettle (Boehmeria spp.)
Where can I see it? Almost anywhere. On buildings, local parks, gardens…
We have seen territorial males on the side of the Academy of Natural Sciences building in Center City.


4) Red-Banded Hairstreak (Calycopis cecrops)

Dorsal view of the Red-Banded Hairstreak
Ventral view of the Red-Banded Hairstreak

Size: Small, about the size of a Raspberry
Generations per year: Two
Overwinter As: Chrysalis (Pupa)

Interesting Facts:
This species has been dramatically extending its range northward in recent decades. It was considered a “visitor” to New Jersey in a 1940 publication but common now in much of the state.

Like other hairstreaks, the hind wings have prominent tails, and the butterfly rubs the hind wings together when perched, giving the impression that the tails are antennae. This is further enhanced by the butterfly doing an 180° spin after landing to confuse predators as to which side is the head. You can see this behavior in the video below.

Note: The video is of a Grey Haistreak (Strymon melinus). Although it not the Red-Banded Haistreak butterfly, which we choose for this guide, the two butterflies are closely related and both butterflies display this same fascinating behavior. (Video by Dr. Jon Gelhaus)
The Red-Banded Hairstreak up close (Photo by Dr. Jon Gelhaus)

What do I plant to encourage it? Sumacs (Rhus spp.) Evidence suggests that larvae may feed on decaying leaf litter underneath sumac (Rhus spp.) but the life cycle is poorly known.
Where can I see it? Forested edges but also in gardens


5) American Copper (Lycaena phlaeas hypophlaeas)

Dorsal view of the American Copper
Ventral view of the American Copper

Size: Small, about the size of a Raspberry
Generations per year: Two to three
Overwinter As: Chrysalis (Pupa)

Interesting Facts:
The name “copper” for this and related species refers to the bright orange colors on the wings. Although named American Copper, this species occurs throughout the Northern Hemisphere, and the European subspecies (L. phlaeas phlaeas) is known as the “Small Copper” in the United Kingdom.

An American Copper rests on the grass and displays its dorsal patterns.
(Photo by Isa S. Betancourt

What do I plant to encourage it? Sheep sorrel, Dock (Rumex spp.)
Where can I see it? Wet meadows and river floodplains where the host plants are abundant.


6) Monarch (Danaus plexippus)

Dorsal view of a male Monarch
Ventral view of a male Monarch

Size: Large, about the size of a grapefruit
Generations per year: One to three broods in the Philadelphia Area. More in the Southern USA.
Overwinter As: Adult (in Mexico)

Interesting Facts:
The common name, the Monarch, indicates the high regard the early lepidopterists held for this butterfly, probably due to its large size, bright orange and black wing pattern, and its reliable summer visits to gardens. In the same name vein, two related southern species are called the Queen and the Soldier, and an unrelated mimic of the Monarch is called the Viceroy!

The Monarch survives the harsh winters of Eastern and Central North America by avoiding the cold weather! The Monarchs we see in late August into October will fly south, up to 3000 miles, to overwinter in a small forested mountain area of Mexico in the fall. Many millions of Monarchs will spend 5-6 months of their life clustered in trees during the cool nights and venturing out on warm days to find nectar. These same butterflies then make their way back to the southern areas of the US to find newly emerged milkweed, the only plants their caterpillars will eat. The adults from those caterpillars, the migrating butterflies’ children and grandchildren, continue north and lay eggs, and eventually make their way into our area as our milkweeds are growing, sometimes as early as May but certainly by July.

How do they have enough energy to make it south to Mexico? They don’t have all that energy in their body – they make use of radiating heat and air currents to glide and conserve energy on their journey.

It may be possible that in the next decades we will no longer see this summer butterfly in our area. The North American Monarch populations are only 10% of what they were 40-50 years ago. Why? Scientists aren’t sure but it is a focus of many research projects. Some possible threats are increased logging of the forests in Mexico, heavier use of herbicides in agricultural fields killing the milkweeds on the crop edges, or possibly newer classes of insecticides. The Monarch has even been proposed for listing under the Endangered Species Act. (While not actually endangered as a species, the North American Monarch populations represent an endangered “migratory phenomenon”). One way you can help is by planting flowers with nectar for the adults and milkweeds for the caterpillars, and to register your garden as a Monarch waystation. We added links to more information on how you can help the Monarch at the bottom of this post in the resources section.

Although a very familiar butterfly here in North America, most people don’t realize that the Monarch has a pantropical distribution; Its distribution spans the tropical areas of both hemispheres of the Earth. The Monarch has only established migratory populations in North America (both east and west of the Rockies, with western populations overwintering in pockets along the coast of California) and in Australia. This butterfly has colonized many tropical islands that were originally devoid of milkweeds after ornamental milkweed species were introduced by man (e.g. The Hawaiian Islands).

Description in the caption
Stages of the Monarch butterfly’s life cycle. Upper left corner: A Monarch egg. Lower left corner: The pupal stage. The chrysalis is bright green with a golden, yellow, and black horizontal band that is about a third down from the top. Center: When the monarch is about to emerge from the chrysalis, the chrysalis becomes transparent and you can see the butterfly’s wings, eyes, antennae, and legs! Right: A Monarch caterpillar feeds on milkweed plants.

What do I plant to encourage it? Milkweeds (Asclepias spp.)
Where can I see it? The easiest time to spot them in Philadelphia is in the early Fall when populations have reached their peak and the adults start migrating south.

A Monarch is on a pink flower in the Logan Square garden. The Academy of Natural Sciences Museum is in the background.
Even outside the Academy of Natural Sciences in Logan Square, you will see a spike in the presence of Monarchs as they start to make their way to Mexico. They stop at the flowers in Logan Square and other butterfly friendly gardens to fuel up along their long journey.
(Photo by Isa S. Betancourt)
Video of a Monarch visiting a flower in Logan Square, Philadelphia. You can see City hall in the background. (Video by Isa S. Betancourt)

7) Sachem (Atalopedes campestris)

In the left column is a male sachem skipper specimen with a dorsal view in the upper image and a ventral view in the lower image. In the right column is a female sachem skipper specimen, also with the dorsal view at the top and the ventral view below.

Size: Small, about the size of a Raspberry
Generations per year: Three
Overwinter As: Chrysalis (Pupa)

Interesting Facts:
As we noted in our last guide, the skippers are named due to their characteristic fast erratic flight. The grass skippers, such as the Sachem, often open their wings partially when at rest, with the hind wings spread further out than the forewings, giving a characteristic “jet plane” wing position. These skippers, like the Sachem, also have a scent patch on the wings of the males called a stigma. You can see the stigma as the dark patch on the forewings of the Sachem. Males perch on or near the ground to look out for females flying by.

This species, like a number we see in the summer, is a southern migrant that recolonizes the northern states each year. Its abundance builds toward the end of the summer into the fall.

There are many similar looking species of grass skippers and they are challenging even for experienced butterfly observers. Even males and females of some species can look quite different from each other. To start, we suggest learning the commonest species in your yard using guides like this, or printed field guides, or by uploading photos to automated identification apps like iNaturalist or Leps. Once you are comfortable recognizing these common species like the Sachem you will notice the rarer visitors to your garden.

A female Sachem skipper feeds on flowers at Bartram’s Garden, Philadelphia. (Photo by Isa S. Betancourt)

What do I plant to encourage it? You probably already have the plants in your yard! Bermuda grass (Cynodon dactylon), crabgrass (Digitaria spp.), and other native grasses
Where can I see it? Disturbed and open areas, gardens, meadows, yards, habitat edges.


8) Cloudless Sulphur (Phoebis sennae)

Dorsal view of the female Cloudless Sulphur
Ventral view of the female Cloudless Sulphur

Size: Medium-small, varies from the size of a lime to the size of an orange
Generations per year: Continuous in the south, they migrate northward in late summer
Overwinter As: Chrysalis (Pupa) in the South. They do not overwinter in this area.

Interesting Facts: This large bright yellow species is named “cloudless” for the lack of dark markings on the wings. It arrives in our area in late summer into fall. It has an extensive breeding and overwintering range from the southeast US into tropical South America and moves north each year in migrating groups, often over the ocean.

A 2001 study followed migrating males and females by boat and found that the movement strategy for males is for them to get to the destination as soon as possible to “greet” the females when they arrive, while the females fly in ways that conserve energy for egg production.

This species is a fast highflier and is not a regular visitor to flowers, so it is hard to closely observe this species. If you see a bright yellow (often with a greenish cast) large butterfly in the fall, obviously in a hurry to get someplace, it is likely the Cloudless Sulphur.

Female Cloudless Sulphur. (Photo courtesy of Jane Ruffin)
A male Cloudless Sulphur that has freshly emerged from his chrysalis.
(Photo courtesy of Jane Ruffin)

What do I plant to encourage it? Sennas (Senna spp.); Cassia spp. (introduced ornamentals grown in southern states)
Where can I see it? Open areas, such as dunes, forest edges and meadows.


9) Pearl Crescent (Phyciodes tharos)

Dorsal view of the Pearl Crescent
Ventral view of the Pearl Crescent

Size: Small, about the size of a cherry
Generations per year: Two to five depending on latitude
Overwinter As: Caterpillar.

Interesting Facts:
This small bright orange and black butterfly is a common visitor to gardens in the summer. It flies low to the ground, with a flight alternating between a series of flaps and glides.

Its common name refers to a small pale crescent mark on the ventral side of the hind wings.

The Phyciodes species complex has required molecular studies to understand the natural hybridization between Pearl Crescent and two more northern species of crescents. Indeed, there has been speculation that there may be more than one species involved under the Pearl Crescent name due to the variation in its coloration. Some variation in wing pattern coloration may represent variation between Spring and Summer generations within a single population. Individual males currenty identified as the Pearl Crescent (Phyciodes tharos) have two different antennal color patterns: most males have black antennal clubs, but some have orange antennal clubs. It is not clear if this is a color polymorphism (variation), or if the less common orange-clubbed individuals might represent an unrecognized “cryptic” species.

There are at least two more very similar Phyciodes species that have been documented in Pennsylvania: P. cocyta (Northern Crescent) and P. batesii (Tawny Crescent). (The latter species has declined in recent decades and may no longer occur in Pennsylvania.)

A Pearl Crescent butterfly pauses on a leaf in the garden. Populations of the Pearl Crescent show different color forms. This shows the orange antennal club form.
(Photo by Isa S. Betancourt)
A Pearl Crescent consumes nutrients from mud. In this image you can see the crescent shapes on the edges of the wing that inspired its common name – the Pearl Crescent. (Photo courtesy of Jane Ruffin)

What do I plant to encourage it? Asters (Symphyotrichum spp.)
Where can I see it? Common in open habitat, including gardens and lawns.


10) Variegated Fritillary (Euptoieta claudia)

Dorsal view of the Variegated Fritillary
Ventral view of the Variegated Fritillary

Size: Medium-small, about the size of a Lime
Generations per year: Three
Overwinter As: Chrysalis (pupa) in South, does not overwinter in our area.

Interesting Facts: Like some other southern species that don’t overwinter in our area, the Variegated Fritillary generally arrives starting in June and more visible in late summer into fall. These butterflies fly low to the ground.

A study of the Variegated Fritillary has shown that butterflies can carry much more than just pollen from flower to flower. The researcher found a variety of different fungal species spores that were being carried around on the bodies of the butterflies.

A Variegated Fritillary rests on the ground. (Photo by Dr. Jon Gelhaus)

What do I plant to encourage it? Violets (Viola spp.) and passion vines (Passiflora spp.)
Where can I see it? open fields, gardens


11) Horace’s Duskywing (Erynnis horatius)

Dorsal view of Horace’s Duskywing
Ventral view of Horace’s Duskywing

Size: Small, about the size of a cherry
Generations per year: Two
Overwinter As: Fully Grown Larva

Interesting Facts:
This species is very similar in appearance to Juvenal’s Duskywing, covered in the late spring guide. Although both can be found in early spring, Horace’s Duskywing is the species found also in summer.

Males of some butterfly species like Horace’s Duskywing seek out high spots in the landscape to encounter females, in a behavior called hill-topping. Entomologists know to climb to the tops of these isolated hills to study these species.

A Horace’s Duskywing skipper lands on a thistle to feed at Paine’s Park, Philadelphia. (Photo by Isa S. Betancourt)
A Horace’s Duskywing perches on a stick in a flower bed at Paine’s Park, Philadelphia (Photo by Isa S. Betancourt)

What do I plant to encourage it? Native oaks (Quercus sp.)
Where can I see it? Open woodlands, meadows, and edge habitat like roadsides. You can find them at Paine’s Park on the Parkway near the Art Museum enjoying the thistle flowers.


12) Common Buckeye (Junonia coenia)

Dorsal view of the Common Buckeye
Ventral view of the Common Buckeye

Size: Medium-small, around the size of a Lime.
Generations per year: Two to three
Overwinter As: Chrysalis (pupa) in south, infrequent overwintering of adults in our area.

Interesting Facts:
The Common Buckeye is distinctive and easily identified, with its prominent large and small multicolored eyespots on each wing, and pair of bright orange bars on the mid-forewing. When the butterfly closes its wings though, the butterfly becomes inconspicuous, as the brown tones of the ventral side of the wing matches the ground. This species is particularly common in late summer into fall and moves south in large numbers along the coast as winter approaches. Males are territorial, perching on bare ground patches and low vegetation and flying out to meet anything that passes.

The Common Buckeye visits goldenrod flowers. (Photo by Dr. Jon Gelhaus)
From certain angles you can catch a glimmer of the Common Buckeye butterfly’s iridescent blue scales, which are in the eyespots on their wings. (Photo by Isa S. Betancourt)
The caterpillar of the Common Buckeye (Photo by Dr. Jon Gelhaus)

What do I plant to encourage it? Narrowleaf plantain (Plantago lanceolata) and Snapdragon (Antirrhinum spp.) are commonly used.
Where can I see it? Open meadows, dunes, also gardens and parks. Very common along the New Jersey coast during fall.


Resources: 

If you like photographing butterflies, you see and want help with identifying them, you might enjoy this app for your phone which has a built-in algorithm to identify the species from a photo you take.
In fact, the specimen images you see in this blog are a part of the pool of images used to calibrate the artificial intelligence that does the image identification.
Download and try out the app, “Leps” today!  https://leps.fieldguide.ai/ 

You can also identify and record your photo observations through iNaturalist https://www.inaturalist.org/  


If you want a paper field guide to have around the garden or out on your walk, we recommend this one for this region: 

A Field Guide to Eastern Butterflies (Peterson Field Guide Series). By Paul A. Opler In paperback. 512 pp. Houghton Mifflin Harcourt. ISBN: 0395904536 
https://www.barnesandnoble.com/w/a-field-guide-to-eastern-butterflies-roger-tory-peterson/1119268694 
If you choose to purchase through Amazon, consider purchasing through AmazonSmile. Amazon will donate .5% of your purchase amount to the Academy if you designate us as your preferred charity. Now, we know that .5% doesn’t sound like a lot—but it adds up! 

References with more information on butterflies for our region: 

To learn more about the plight of Monarchs: https://monarchwatch.org/index.html
Contribute your Monarch sightings to Journey North: https://journeynorth.org/monarchs
The Xerces Society for Invertebrate Conservation’s page on Monarchs:
https://xerces.org/monarchs

For the most recent sightings of butterflies in New Jersey check out the South Jersey Butterfly Project https://sjbutterflies.org/ 

Butterflies of Pennsylvania: A Field Guide. 2017, by James L. Monroe and David M. Wright. In paperback. https://upittpress.org/books/9780822964551/  

Butterflies of New Jersey.  1997. by Michael Gochfeld and Joanna Burger.  In paperback.  https://www.amazon.com/exec/obidos/ISBN=0813523540/103-2305405-0687859  

Butterflies of the East Coast: An Observer’s Guide. 2007. by Rick Cech and Guy Tudor. In paperback. Princeton Univ. Press.  https://smile.amazon.com/Butterflies-East-Coast-Observers-Guide/dp/0691090564 

Butterflies & Skippers (Lepidoptera: Papilionoidea, Hesperioidea) of the Franklin Parker Preserve, Burlington County, New Jersey. 2015. By Stephen C. Mason Jr. Transactions of the American Entomological Society, 141(3):351-368 download http://taes.entomology-aes.org/modules/articles#/manuscripts  

Butterflies and Moths of North America:   https://www.butterfliesandmoths.org/

Study on the Cloudless Sulphur’s migration journey:
https://academic.oup.com/beheco/article/12/5/607/311694


Content by Academy Entomologists:
Isabelle Betancourt, Jason Weintraub, Dr. Jon Gelhaus

7 comments

  1. I sent an email about 2 hrs ago regarding this site and wondering why “you” did not make a pdf of the guide.

    So I did.

    If you send me an email address, I’ll rsvp this edition of the pdf and can change it to your liking.

    1. Thank you for your kind offer, Dr. Wm. Saidel,
      Our graphic designer made the last two guide PDFs and will make one in the same format for this guide too. However, they have been swamped with he reopening of the museum and they are also on vacation this week.
      We will have our PDF version out soon.

    1. Hi David, thank you for taking the time to comment. The dorsal and ventral Monarch images are of the same specimen.

  2. I didn’t have my phone with me to get a picture but yesterday I saw a huge Albino Monarch busily feasting from my purple butterfly bush. Beautiful! First time I’ve seen one. Am in Lower Bucks County, 19055..

    1. Monarchs and other species of Danaus butterflies have populations with varying degrees of polymorphism. The white form is an autosomal recessive trait (like cystic fibrosis or sickle cell anemia in humans). White monarchs have been studied in the Hawaiian Islands where they are much more common (especially on the Big Island). There is paper about white monarch that is accessible via the Biodiversity Heritage Library – see the following URL : https://www.biodiversitylibrary.org/page/53319502#page/165/mode/1up
      [Stimson & Meyers (1984) Inheritance and frequency of a color polymorphism in
      Danaus plexippus (Lepidoptera: Danaidae) on Oahu, Hawaii. J. Res. Lepid. 23: 153-160.]

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