On September 4, Chris Lindsey photographed a very small brown-blue butterfly near Highway 12 in Walla Walla County. Excitingly, it turned out to be an individual of the smallest butterfly species in North America, the Western Pygmy Blue!

The Western Pygmy Blue (Brephidium exilis) was added to the list of Washington butterflies back in 2004, when Bob Pyle found it on the WA side of the Columbia River in Benton County. However, prior to this year, there had only been a handful of records in WA, all close to the Columbia.

As I write in late October, Pygmy Blues have been found in at least 25 locations along the Columbia, Snake and Yakima Rivers as far north as Horn Rapids, more than 30 miles from the OR/WA state border. Currently, there are 34 reports with photos of WA pygmies on the iNaturalist web site and Caitlin LaBar and Jon Pelham have had more than 70 sightings reported to them!

There has been a remarkable explosion of interest in this minutest of butterflies not only from lepidopterists but also ornithologists, botanists and Audubon Society members. In other words, naturalists of all persuasions have joined ranks to find and record this butterfly. A remarkable event indeed! The Pygmy invasion even attracted the attention of the Tri-Cities Herald and NPR who both provided excellent coverage.

Most Pygmy Blue sites have small populations, less than a dozen individuals, but when I became aware of one site that apparently had a population of hundreds, I knew it was time for an October surprise WBA “flash” field trip.

Most sightings have occurred in the Tri-Cities area in degraded habitats where tumbleweeds (Russian Thistle) and rabbitbrush are common. The former is a caterpillar host plant and the latter is an important nectar source for all October butterflies in eastern WA.

So, with just a week‘s notice, 20 WBA members and a few Tri-Cities botanists and birders, gathered on Friday October 7 near the Yakima River west of Richland. I boldly guaranteed that we would see Pygmy Blues! Such is the draw of this miniscule butterfly that we had people from Seattle and Portland drive many miles to join us!

The Pygmy Blues did not disappoint! They could be seen flitting in their dozens over tumbleweeds in the parking lot, before we even got out of our cars. One tumbleweed in particular, located adjacent to a porta-potty, was the champion in the Pygmy Blue attraction stakes, with maybe 20 or more!

It was a remarkable sight: a dozen or more butterfly people all gathered around a porta-potty with cameras and binoculars looking for this wisp of a butterfly.

Now that November is here and winter beckons, what is the future for this tiniest of butter- flies in Washington? The Pygmy Blue is a species that extends its range north every summer, then contracts in the winter to more southerly climes. It does not have an overwintering stage with a diapause as all resident Washington butterflies have.

Although it is conceivable Pygmy Blues could survive a mild Washington winter especially in a warmer microclimate near a river, it is unlikely to establish itself as a year-round resident anytime soon. However, it may well become a more frequent late summer/autumn visitor to Washington as its overwintering range extends further north and WA summers become warmer and longer.

I will be monitoring the porta-potty population of Pygmies for the remainder of the fall then will check the location in spring to see if any did actually survive the winter. Perhaps we will be able to have another field trip in 2023, if you missed out on seeing this princely pygmy butterfly!

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