Pygmy Blue
Another New Washington Butterfly

Brephidium exile

Order Lepidoptera, Family Lycaenidae

Copyright © 2004 by  Robert Michael Pyle

This article originally appeared in Scarabogram, October 2004, New Series No. 294, pp. 3-4; with corrections in November 2004, No. 295, p. 2.

On September 17, 2004, a new butterfly joined the Washington butterfly checklist: the Pygmy Blue, Brephidium exile = exilis. First, I must thank Andy Warren for tipping us off to Neil Bjorklund's great recent find of the butterfly at the Umatilla National Wildlife Refuge in Morrow County, Oregon, a substantial range expansion northward. Andy exhorted us to go forth and seek the butterfly for a Washington state record. So this successful search really owes to those two gents.

pygmy blue butterfly, Brephidium exile
Brephidium exile, Arizona, October 1999
© Idie Ulsh, used with permission

I left Gray's River Thursday afternoon and camped along the Columbia below Paterson, Benton County, opposite the Umatilla NWR's Oregon unit. I retired beneath starry skies, in warm air alive with early autumn insects, with high hopes for a sunny morning. About the fifteenth time I awoke to a train, the sky was pale--and very gray. Friday began under a damp overcast with off-and-on rain, the forecast seemingly advanced by several hours. A chilly walk revealed a moribund orange sulphur tucked into a Russian thistle, giving some hope for finding some sheltered butterflies at least.

The pygmy blue is an emigratory species, resident throughout the Great Basin and around the Gulf, where it feeds on saltbush, Russian thistle, and various other native and weedy chenopods. In summer it expands northward like many other species, producing opportunistic generations until a killing frost knocks them off. The previous northernmost record in Oregon was a hundred miles south. It has long been on our list of a species to watch for in Washington, and the species' appearance on the Columbia suggested to Andy that it might have reached Washington as well this year. Umatilla NWR spans the Columbia at one of its narrowest points in Washington, so it seemed the river might not prove an insuperable barrier to such a wide wanderer--despite its minute size. B. exile is the smallest butterfly in North America, one of the smallest in the world, about a half-inch in wingspan. Even Leona's little blue, which Thea and I managed to see on the Mazama volcanic sands east of Crater Lake this summer, is bigger by comparison! The butterfly can be difficult to see, perhaps leading to our few records.

All day I worked the abandoned (pre-dam) railroad line above the river, east and west of Paterson, and other likely habitats. I was looking especially for blooming rabbit brush (both Chrysothamnus nauseosus and C. viridis) in the vicinity of Russian thistle (= tumbleweed or wind witch, Salsola kali): the former is a great nectar plant for pygmy blues, the latter a common larval host. There was plenty of each, though most of the rabbitbrush was not yet in full bloom. It has a large arthropod fauna associated with it, so I had marvelous insect watching: colorful blister and longhorn beetles, big flat-black Neoscona orb-weavers, lots of bees, wasps, and flies (leading to many false alarms), ant lions, dragonflies, and some handsome leps: nectaring sphingids, geometers and noctuids, including a small, orange-underwinged noctuid (Pseudanarta crocea, later identified by Lars Crabo after an initial misidentification by me). Several white-lined sphinxes (Hyles lineata, another immigrant that has been numerous this year) nectared on rabbitbrush and on the tiny flowers of snow buckwheat (Eriogonum niveum), proving they do not solely favor deep-throated flowers after all; I found its larva feeding on a small-flowered Epilobium.

Birding too was rewarding, notably the massive and graceful white pelicans, and four or five great egrets, which I didn't even know we had except as strays--another species moving north. But my quarry was smaller than the eyes of those big birds, and it remained coy. Most of the day had been cloudy and cool, with spitting rain. Of butterflies, popping up in brief sun-spots, I saw just one Juba skipper, one probable woodland skipper, and a sole monarch sailing over a goldenrod marsh (both species of milkweed, Asclepias speciosa and A. fascicularis, were present on the Paterson Unit of the Umatilla NWR). I'd hoped for the autumn Acmon blues and Mormon metalmarks on the snow buck-wheat, but no go. So much, it seemed as the day waned, for pygmy blues.

Then, just before six p.m., as I headed back along the old rail line east from the refuge boundary, I spotted a patch of rabbitbrush in bloom, and decided to check it out. The clouds were thinning and now the sun actually came out. I began to descend into a forbidding swale of Russian thistle, when I detoured for a rabbitbrush off to my left, and tapped a tumbleweed on the way. Out popped a tiny insect that glittered. "That's it!" I told myself, and when it alighted on a nearby bitterbrush, I glassed it and saw that it was so. Marsha (my net) went into action and caught it. As it was a male of an adventitious species that would not persist for the winter, I collected the voucher specimen. My, it was tiny! A rainbow crossed the Columbia in the east (really), and in the west the sun set brilliantly as if it had been out all day. I followed a slender crescent moon down the Columbia, pausing for a good Walking Man IPA in Stephenson, and climbed into bed at two a.m. 38 hours, 550 miles, five butterflies, one new state record. While I was shaking Salsola in Benton County, Thea had been gathering baskets of chanterelles in the woods back home: a good day for each.

It is interesting to note that of the five new Washington butterflies in whose discovery I've been lucky to take part, two were annual immigrants, two were fresh colonists, and one an overlooked indigene. The golden hairstreak (1980) turned up as soon as we found the golden chinquapins in Skamania County (I looked again at the Hood Canal chinquapins this year, with Kristi Knowles; and though the trees were robust in one area, we found no sign of H. grunus). Sachem skippers (1990) and European Skipperlings (2002) have both colonized our fauna, the former from the south, the latter from the north. Dainty sulphurs (1975) and pygmy blues (2004) have reached the state at least once in their annual expansions, before dying back. As the climate warms up, we can expect to see more and more of these emigratory arrivals. For example, we have had two California Sisters in our garden this summer--the 6th & 7th records for Washington.

With the addition of the pygmy blue, the Washington butterfly fauna now stands at somewhere between 145 and 150. The total depends on questions such as these: Do we have both Lupine and Acmon blues, and is P. spangelatus a distinct species? How many species of Euphilotes dotted blues occur here? How many entities do our spring azures/echo blues represent--one, two, or three? Do we have both Atlantis and Northwest (S. hesperis) fritillaries? Afranius dusky-wings? Canada swallowtails? And, do we count the ancient record of a zebra butterfly, Patti Ensor's eastern-type white admiral that probably came in on a camper, and a neat record I recently received from reliable observer Barbara Laudan of a Buckeye well-spotted in Longview in 1953? Several other species are no doubt lurking just inside our borders, or will arrive next year. Let's go find them!


Pyle, Robert M. 1999. Chasing monarchs : migrating with the butterflies of passage. Houghton Mifflin, Boston, 307 pp.

_____. 2002. The butterflies of Cascadia : a field guide to all the species of Washington, Oregon, and surrounding territories. Seattle Audubon Society, 420 pp.

Web pages on this species:
at Butterflies of North America (WA record finally included)
at Sonoran Arthropod Studies Institute
at Digital Atlas of Idaho

This page last updated 24 July, 2006