Western Pygmy Blue: Quick Guide to These Tiny Marvels

The Western Pygmy Blue is a fascinating butterfly that you might not know much about. This tiny creature has been catching the attention of butterfly enthusiasts for years due to its unique appearance and habits. As you explore the world of butterflies, it’s essential to learn more about this little beauty.

With a wing span of just ½ – ¾ inch (1.2 – 2 cm), the Western Pygmy Blue is one of the smallest butterflies you’ll encounter. Its delicate wings showcase a combination of coppery brown and dull blue, making this species easily distinguishable from others. As we delve into the world of the Western Pygmy Blue, you’ll discover some interesting facts about its habitat, behavior, and conservation efforts.

Western Pygmy Blue: A Brief Overview

The Western Pygmy Blue (Brephidium exilis) is one of the smallest butterflies in the world. As a member of the Lepidoptera order, it belongs to the Blues family, which is characterized by their small size and vibrant coloration. In this brief overview, we will introduce you to the Western Pygmy Blue and some of its fascinating features.

This tiny butterfly has a wing span of just ½ – ¾ inch (1.2 – 2 cm) and displays a coppery brown color on its upperside (dorsal) with a hint of dull blue at the bases of both wings. The underside (ventral) of the hindwing exhibits a coppery brown with white at the base, and its fringe is mostly white with three or four small dark spots near the body and a row of black spots with metallic accents (source).

The Western Pygmy Blue can often be found fluttering weakly around its larval food plants. Despite their small size, these butterflies can sometimes be observed in large numbers. Their distribution is especially abundant in coastal areas, though they also occur less commonly in interior regions (source).

Overall, the Western Pygmy Blue is a remarkable butterfly that stands out for its small size and striking coloration. Its unique characteristics make it a captivating member of the Lepidoptera order and a true tiny gem in the Blues family.

Physical Characteristics


The Western Pygmy Blue butterfly, scientifically known as Brephidium exilis, is a tiny species that displays a unique combination of colors on their wings. Let’s take a closer look at the physical characteristics of both males and females, as well as caterpillars and pupae.

Males and Females

  • Wingspan: Both males and females have a wingspan of ½ – ¾ inch (1.2 – 2 cm), which is quite small compared to other butterfly species.
  • Upperside: The upperside of their wings (also called the dorsal side) is coppery brown with dull blue at the bases of both wings.
  • Underside: The underside of their wings (also called the ventral side) features a coppery brown color with white at the base.

Caterpillars and Pupae

  • Caterpillars: Not much is known about the specific physical characteristics of Western Pygmy Blue caterpillars.
  • Pupae: Similarly, little is documented about the physical appearance of their pupae.

Wing Patterns

An intriguing aspect of the Western Pygmy Blue’s wings is the presence of distinct black spots and patterns.

  • Hindwing: On the underside of the hindwing, you can observe three or four small dark spots near the body.
  • Row of black spots: The hindwing also sports a row of black spots with metallic scales within them.
  • Fringe: The fringe of their wings is mostly white, adding a delicate contrast to the overall coloration.

Remember, when observing these delicate creatures in their natural habitats, handle them with care and allow them to continue their important role in the ecosystem. Enjoy the beauty of the Western Pygmy Blue while respecting their natural environment and delicate nature.

Distribution and Habitat

North America

The Western Pygmy-Blue butterfly (Brephidium exilis) thrives in various habitats across North America. They are found in a wide range, from Florida to California, and from Mexico to Arizona. Also, they are commonly seen in the states of Alabama, New Mexico, and Texas.

Their preferred habitats include deserts, alkaline areas, and salt marshes. Specific habitat characteristics include:

  • Open spaces with little vegetation
  • Areas with plenty of available larval host plants
  • Regions with mild to warm climates

In these environments, Western Pygmy-Blue butterflies find the resources they need to flourish.

International Presence

While the Western Pygmy-Blue butterfly is native to North America, it also has an international presence. Travelers from North America have introduced these tiny butterflies to various regions around the world. Today, you’ll find them in:

  • Western Pacific Ocean islands
  • Saudi Arabia
  • Australia

Despite their overseas travels, their preferred habitats remain consistent. They still thrive best in deserts, alkaline areas, and salt marshes. So, when you’re exploring the Western Pygmy-Blue’s distribution and habitats across the globe, remember to keep an eye out for their favorite living conditions.


The lifecycle of the Western Pygmy Blue (Brephidium exilis) is an interesting one that you should know. Its small size and unique characteristics make it a fascinating species to study.

Brephidium Pseudofea

First, let’s talk about the subspecies Brephidium pseudofea. Although it’s closely related to the Western Pygmy Blue, there are some differences in appearance and habitat preferences. For instance, Brephidium pseudofea is found in more coastal areas whereas the Western Pygmy Blue can be found in both coastal and interior areas1.

Overwintering Stage

Now, let’s discuss the overwintering stage in Western Pygmy Blue’s lifecycle. Like many other butterfly species, they go through a dormancy period during the colder months. Overwintering helps the Western Pygmy Blue survive harsh weather conditions and improves their chances of reproducing once spring arrives2.

Lifecycle Stages

The different stages of the Western Pygmy Blue’s life include:

  • Eggs: The Western Pygmy Blue lays its eggs on the host plants where the larvae will feed3.
  • Larvae: Once the eggs hatch, the larvae feed on the leaves of the host plants to grow and develop3.
  • Pupae: After the larval stage, the Western Pygmy Blue forms a pupa or chrysalis. Inside, it undergoes a transformation, known as metamorphosis, before emerging as an adult3.
  • Adults: Finally, the adult Western Pygmy Blue emerges from the pupa, ready to mate and continue the lifecycle3.

With this information, you can appreciate the complex and fascinating lifecycle of the Western Pygmy Blue.


Host Plants

The Western Pygmy Blue butterfly mainly relies on plants for its nourishment, both as a caterpillar and an adult butterfly. As a caterpillar, it feeds on specific host plants for growth and development. As an adult butterfly, it looks for nectar plants to obtain essential nutrients.

Adult Western Pygmy Blues prefer nectar from flowers, which provides them with vital energy. You may observe them feeding on various types of flowers, enhancing the pollination process. They are not limited to one type of nectar plant, giving them a diverse choice to select from.

The caterpillars, however, are more selective in their habitat and feeding choices. They primarily rely on plants belonging to the goosefoot family (Chenopodiaceae). Host plants commonly include saltbush species in the Atriplex genus and pigweed, or Chenopodium album. These plants provide important nutrients needed for the caterpillar’s survival and transformation into a butterfly.

Host plants play a significant role in where Western Pygmy Blue butterflies choose to lay their eggs. Female butterflies look for appropriate host plants to ensure that, once hatched, their caterpillars have immediate access to their preferred food source.

In summary, the diet of Western Pygmy Blue butterflies encompasses two primary types of plants:

  • Nectar plants: as an adult butterfly, feeding on various flowering plants
  • Host plants: as a caterpillar, specifically feeding on plants in the goosefoot family, such as saltbush species and pigweed

By understanding the dietary preferences of the Western Pygmy Blue, you can appreciate the delicate balance between butterfly populations and their preferred plants. Observing these butterflies in their natural habitat highlights the interconnected relationship they have with their surroundings, and their importance in maintaining a healthy ecosystem.

Migration and Sightings

The Western Pygmy Blue butterfly can be sighted in various locations throughout the year. You may be interested in using websites like iNaturalist and Butterflies and Moths of North America to discover and record sightings.

These tiny butterflies are typically active during the warmer months of the year. You might notice them more frequently between August and November. Due to their size, they can be difficult to spot, but their distinctive coppery brown and blue coloration on the wings can help you identify them.

Some resources you can explore to learn more about this species include the Animal Diversity Web and Alabama Butterfly Atlas. They provide information on the Western Pygmy Blue’s habitat, behavior, and feeding preferences. Lepidopterists—people who study butterflies and moths—also contribute valuable knowledge about these fascinating creatures.

Remember to keep your eyes peeled for these small wonders during their peak activity months. With a bit of patience and a keen eye, you’ll be able to spot the beautiful Western Pygmy Blue and appreciate the intricate details of this extraordinary butterfly.

Comparative Study

Blue Whales

When it comes to comparing the Western Pygmy Blue butterfly with the Blue Whale, you may be surprised to find some interesting facts about these vastly different species. Despite their size differences, both the Western Pygmy Blue and the Blue Whales are part of the Animal Kingdom. The first difference you might notice between these creatures is their respective sizes. The Western Pygmy Blue is a tiny butterfly, with a wingspan of just ½ – ¾ inch (1.2 – 2 cm) 1. On the other hand, the Blue Whale is the largest animal on Earth, reaching lengths of over 100 feet (30 meters) 2.

Some primary features of the Western Pygmy Blue include:

  • Coppery brown upperside
  • Dull blue at wing bases
  • Coppery brown underside with white fringe
  • Row of black spots on hindwings with metallic scales1

While primary features of Blue Whales include:

  • Massive size and streamlined body shape
  • Blue-grey colored skin
  • Baleen plates in their mouth to filter food
  • Long pectoral fins, and a small dorsal fin on their back2


The Western Pygmy Blue is an insect, specifically a butterfly. Insects are a diverse group of animals, consisting of more than a million species 3. Some insects share characteristics such as having a three-segmented body, three pairs of legs, and two antennae. The Western Pygmy Blue is a great example of an insect bearing these characteristics, with a small, compact body, and delicate wings.

Comparing the Blue Whale to insects in general, you will notice significant differences. Whereas insects are invertebrates with a hard exoskeleton, mammals, like Blue Whales, have a backbone and a soft outer covering of skin. Another contrast lies in their habitat; insects are mostly terrestrial and found on every continent, while Blue Whales are marine animals inhabiting the Earth’s oceans2 4.

Feature Western Pygmy Blue Blue Whale Insects
Living Env. Land Ocean Land
Body Structure Invertebrate Vertebrate Invertebrate
Size Small Massive Varies

Understanding the differences between the Western Pygmy Blue, Blue Whales, and insects offers a fascinating insight into the immense diversity of life on our planet.

Conservation and Threats

As a lover of nature, you might be curious about the conservation efforts surrounding the Western Pygmy Blue. This tiny butterfly is considered a pollinator, which means they play an essential role in our ecosystems by helping plants reproduce.

Fortunately, the Western Pygmy Blue is not currently listed as a threatened species. However, it’s still essential to be aware of potential threats to their habitats. Some possible dangers include pesticide use, habitat loss or fragmentation, and climate change.

To help support their conservation, you can:

  • Plant native flowers in your garden to provide food and habitats for the Western Pygmy Blue and other pollinators
  • Be cautious with pesticide use, especially when it’s close to butterfly habitats
  • Support local and global conservation organizations working to protect pollinators and their habitats

By implementing these practices, you’re contributing to the preservation of these tiny but essential creatures, ensuring their positive impact on our environment.


  1. Pygmy Blue, Brephidium exilis – University of California, Irvine 2 3

  2. Western Pygmy-Blue – Alabama Butterfly Atlas 2 3 4

  3. ECOS: Species Profile – FWS 2 3 4 5

  4. Insect Habitat – Insectlopedia

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Western Pygmy Blue in Mount Washington


Western Pygmy Blue
Location:  Mount Washington, Los Angeles, California
June 24, 2014 5:00 PM
While taking some images of the California Harvester Ants, we noticed a butterfly so small it could only be a Western Pygmy Blue.  Our images are not as nice as Anna’s are, but they do document this lovely diminutive butterfly in Mount Washington.

Western Pygmy Blue
Western Pygmy Blue

The Western Pygmy Blue is the smallest butterfly in North America.

Western Pygmy Blue
Western Pygmy Blue

Letter 2 – Western Pygmy Blue: North America's Smallest Butterfly


World’s Smallest Butterfly
Location: Hawthorne, CA
November 7, 2011 11:27 pm
I was able to identify this tiny guy (about the size of a bottle fly) out at Bugguide today and thought I’d share it with you. It sat for about fifteen minutes feeding on the Bishops Flowers in the back yard. Such a little beauty. I’ve read it is the world’s smallest butterfly.
Signature: Thanks, Anna Carreon

Western Pygmy Blue

Hi Anna,
Your photos of a Western Pygmy Blue,
Brephidium exilis, are quite lovely.  Thanks so much for supplying our site with this new species and a statistic as well.  According to Charles Hogue in Insects of the Los Angeles Basin:  “This is one of the world’s smallest butterflies;  the wing expanse of even the largest individuals barely exceeds 1/2 inch (13 mm). … The Pygmy Blue is seen mainly in wild areas, especially where the salt-loving food plants grow – in alkaline valleys and flats, in coastal salt marshes, and along beach bluffs.”  Jeffrey Glassberg, in his book Butterflies Through Binoculars The West, writes:  “The smallest butterfly in North America.”  According to BugGuide, the Western Pygmy Blue is ” The smallest butterfly in our area.”  We are not certain where your smallest butterfly in the world statistic came from.

Western Pygmy Blue

Hi Daniel,
Thanks for the compliment.  I read about it being the smallest in the world in a few places, none of them specialists in butterflies.  I used that subject title because I was sure it would catch your eye!

Ed. Note:  We wonder how it was determined that the Western Pygmy Blue is the smallest butterfly in North America.  Was it an average?  or perhaps, was it the smallest individual documented?

Letter 3 – Western Pygmy Blue rescued from swimming pool


Location: Merced, CA 95340
April 7, 2012 10:18 am
Last year, this butterfly was in my swimming pool. I got it out and let it sit in the sun for a few minutes and it was able to fly away. I don’t think I’ve seen one before, curious what it might be.
Signature: T. Tanioka

Western Pygmy Blue

Dear T. Tanioka,
Your butterfly is the smallest butterfly in North America, the Western Pygmy Blue,
Brephidium exilis, as you can see from this matching photo on BugGuide.  Because of your rescue efforts, we are tagging you as a Bug Humanitarian.


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

2 thoughts on “Western Pygmy Blue: Quick Guide to These Tiny Marvels”

  1. They are so tiny. You have to be out there to even see them. They like tumbleweeds.
    Usually, when i see them, it means go home old fool.

  2. They are so tiny. You have to be out there to even see them. They like tumbleweeds.
    Usually, when i see them, it means go home old fool.


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