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Pygmy Blue Butterfly

What is the Smallest Butterfly? Your Guide to the Western Pygmy Blue Butterfly

There are more than 17,000 butterfly species and they live on every continent except Antarctica. In many locations, they have adapted to their ecosystem with unique behaviors and physical changes, but what is the smallest butterfly? The Western Pygmy Blue butterfly is one of the smallest butterflies in the world and this species is the focus of this article.

A butterfly is a wondrous and fragile creature to observe, they don’t live long, but they have a fascinating lifecycle and they pack a lot into a short period of time. The average adult butterfly may only live a few weeks, but this gives their existence a poignancy that can give us valuable insights into our own lives.

What Is A Western Pygmy Blue Butterfly?


Western Pygmy Blue Butterfly on a Strawberry plantIt’s hard to observe this species in the wild because it’s small and a fast and evasive flier. Most people only catch a brief glimpse of a blue wing before the Western Pygmy Blue butterfly (brephidium exilis) leaves their peripheral vision.


This butterfly belongs to the Lycaenidae family and Polyommatinae subfamily. It can be identified by the dull blue base at the wings and a copper/brown dull underside which is white at the base.


There are three tiny black spots near the base of the wings and a second row near the outer margins.

How Small Is A Western Pygmy Blue Butterfly?


The Western Pygmy Blue is a common butterfly, but it’s approximately the size of an adult man’s pinky finger nail. It’s also not an especially bright blue color and it’s easier to recognize them by their rounded brown/copper and fringed gray wings.

These butterflies can be found perching and hovering in saltbush.


What Are The Features Of A Western Pygmy Blue Butterfly?


The wings are a distinctive copper/brown color with a metallic blue section on the part of the wing closest to their body. The white/gray edges on the wing edges and dots of small white flecks on the underside are distinctive.

But, these features are hard to spot unless you’re lucky or you set up near some salt-bush to observe them.


Where is The Pygmy Blue Butterfly Found?


As we mentioned earlier, the Western Pygmy Blue butterfly is partially blue, but the color is not its standout feature. But, the name is at least somewhat accurate because these butterflies are usually found along the western coastlines of the United States.


This area stretches from Oregon in the north right down to Mexico and even Venezuela.

The concentration of the Pygmy Blue tends to lessen as you travel further south. These butterflies tend to inhabit desert, salt marsh and wasteland areas. But, they will venture further afield if they can find saltbush, pigweed, seepweed, and horse purslane food sources.


At this time we don’t know why the Pygmy Blue prefers these areas and further study is needed.


What Does the  Western Blue Pygmy Butterfly Eat?


The Western Pygmy Blue butterfly follows the same life cycle of other species. The caterpillar emerges from an egg, it then eats voraciously to grow rapidly and form a chrysalis. Inside the chrysalis dramatic changes take place and the butterfly emerges.


A short rest period to move the blood into the wings and dry them is followed by the first flight within an hour. The butterfly will then search for food and a mate to breed with.


For food, the caterpillars will eat from the host plants mentioned above. There are some regional variations, in the southern states the American Glasswort and Southern Seablite are thought to be host plants too. The caterpillars will eat the plant matter and butterflies drink the nectar of the flowers.


Western Blue Pygmy Butterfly Breeding:


The Western Pygmy Blue butterflies don’t have a set breeding season like certain other species. But, the mating activity is known to reach its peak during the late summer and early fall months.


The female will lay two, three or four broods of eggs after they’ve mated with a suitable male. The eggs will be laid on one of the host plants we mentioned earlier to ensure that the caterpillar has a ready source of food when they emerge.


The Pygmy Blue caterpillars are yellow/green in color with a pattern of tiny brown spots on the body. They will live on their host plant for a short-time as they bulk up for the transition ahead.


When they reach the right size and weight the caterpillar pupates and completes the metamorphosis into a Western Pygmy Blue butterfly.


Is the Western Pygmy Blue endangered?


smallest butterflyThankfully no, it is pretty common across the entire natural range down the West coast of the United States. But, the most populous areas are the Southwestern areas from California to the East into West Texas and then down into Mexico and Venezuela.


The migrations to Oregon, Nebraska and Arkansas are fairly common and close observations of host plants in these areas is a great place to find them. In recent years the species has been introduced to Bahrain, the United Arab Emirates, Eastern Saudi Arabia and up the Persian Gulf into Kuwait.


Interesting Facts About The Western Pygmy Blue Butterfly


  • The Pygmy Blue is easiest to spot in the late summer and early fall months when the breeding activity tends to reach its peak.
  • This butterfly species is extremely hardy, it can fly during spring and through fall and up to four broods can be produced each year.
  • Individuals are hard to spot, but you can see clouds of butterflies looking for mates or food in and around the host plants.
  • The Pygmy Blue will not spend much time lingering on food sources or sunning themselves and this has given them a reputation as a “nervous flier”.
  • These butterflies are adaptive and can be successfully introduced to new climates if there are sufficient sources of food for them.
  • Western Pygmy Blue butterfly can range from ½” up to ¾”.
  • The male has darker coloration than the female with prominent dark blue highlights and white edges on the wings.
  • Females are usually larger than the males, but this can vary depending on the specific habitat.



The Western Pygmy Blue butterfly is considered to be the smallest species, but there may be individuals from other species that could be as small or even smaller.

Some close contenders include: 

  • North American Brephidium Pseudofea,
  • Tongeia Minima from China, the Micropsyche Ariana from Afghanistan,
  • Barberae from Southern Africa
  • Others which are all Blue butterflies.



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