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Silverspotting

Updated: Aug 17

The Oregon Silverspot (Argynnis zerene hippolyta) is a subspecies of the Zerene Fritillary (Argynnis zerene), found along the Oregon coast and in the Coast Range, in just a few locations. It's one of two butterflies whose common name includes "Oregon," and it's one of three butterflies found in Oregon that are protected under the Federal Endangered Species Act. The Oregon Silverspot is listed as Threatened under the ESA, and its habitats along the coast are protected under that law.


If you pay attention to latin names of butterflies, right about now you might be thinking "hey, wait a minute--Argynnis zerene? Where did that come from? I thought the Zerene Fritillary was in the genus Speyeria!" Well, it was. But then last year, a group of scientists published an article summarizing the taxonomic results from a massive DNA analysis of all North American butterflies (north of Mexico). Their findings have affected the taxonomy (official naming and classification) of 6% of North America's butterflies. Among other findings, they found that the group of butterflies that had been in the genus Speyeria really belonged in the genus Argynnis, because genetically speaking those in the Speyeria group were essentially subspecies of Argynnis. Confusing, I know.


Here in Oregon, we will be seeing these taxonomic changes showing up over the coming months as the various online and printed sources catch up with these recent findings:

  • As describec above, the genus Speyeria becomes Argynnis

  • Most of our coppers change from the genus Lycaena to the genus Tharsalea, giving us Tailed Copper (Tharsalea arota), Ruddy Copper (Tharsalea rubida), Great Copper (Tharsalea xanthoides), Edith's Copper (Tharsalea editha), Blue Copper (Tharsalea heteronea), Gorgon Copper (Tharsalea gorgon), Lilac-bordered Copper (Tharsalea nivalis), Purplish Copper (Tharsalea helloides) and Mariposa Copper (Tharsalea mariposa)

  • Our Ochre orCommon Ringlet is now Coenonympa californica, since it was split from Coenonympa tullia. What is now C. tullia is found in far northern North America and Europe.

  • Our Arctic Skipper is now Carterocephalus skada, having been split from it's former Carterocephalus palaemon and a new species called Carterocephalus mandan.

  • The study also suggests changes to the naming and classification of cloudywings, tortoiseshells, and commas, but there remain some mixed views on those changes at this point.

Okay, now that we have that cleared up (?!), let's get back to our Silverspots! As I wrote last time, after seeing seven species of greater fritillaries in the central Cascades in recent weeks, I was inspired to finally go find and photograph our threatened subspecies of Zerene Fritillary, the Oregon Silverspot. The most robust Silverspot population is up on Mt. Hebo along the Tillamook/Yamhill county line, southeast of the town of Tillamook. It's about a two and a half hour drive from Eugene. With a weather forecast of haze and high heat, I hoped it would be tolerable up on the mountain.


Indeed, when I arrived at about 11 am, it was hazy and already getting hot. My first stop was in a large, dry meadow near some radio facilities in the NW corner of Yamhill County, where I found my first Oregon Silverspot within minutes, nectaring on Pearly Everlasting (Anaphalis margaritacea). I decided to settle down next to a nice patch of those flowers, hoping I could just wait for them to come to me.

Photo of meadows at Mt. Hebo, Oregon
Salal and sword ferns dominate the meadows on Mt. Hebo that support the threatened Oregon Silverspot

However, I found that when I sat very still next to a good nectar plant, the Silverspots virtually never came to that plant, though they would visit other plants nearby. This rendered my preferred "stakeout" tactic essentially useless. Surprisingly, I found that I could walk up slowly to a plant with one or more Silverspots on it and kneel down slowly and they would not fly off.

Close-up photo of adult Oregon Silverspot butterfly
Oregon Silverspot nectaring on pearly everlasting (Anaphalis margaritacea) - Mt. Hebo, Yamhill County

I saw about 20 Silverspots in that first meadow and got some nice photos with my "molasses in winter" approach technique. There were also a number of Woodland Skippers (Ochlodes sylvanoides) and a couple Hydaspe Fritillaries (Argynnis hydaspe) there. At about noon, the sun was getting quite warm, so I took a break, had a snack, and then headed toward the next meadow, just over the county line. My plan was to scout all the meadows just to get to know the area better.


The second meadow was also quite dry, and I found very few nectar plants there. All of the Silverspots were on the move, with females looking for larval host plants (Viola adunca) among the dominant stubby ferns and salal, and males looking for females--no posing Silverspots there! Just as I was finishing my circle through the large meadow, I heard a car pull up behind mine, and then watched a man who appeared to be walking quite purposefully toward me. Immediately, I heard a voice in my mind say "am I getting ticketed for something?" Then I realized he wasn't in uniform, and probably just wanted to chat, so I headed towards him also. As I got closer, I recognized Paul Hammond, Oregon's top fritillary expert coming my way. What great luck!


Paul was close to finishing up his annual two-day survey of the Silverspots, and he offered to show me the hotspots in the area. I couldn't have dreamed up a better chance encounter than Paul, who knows this site and this butterfly better than anyone else.


Close-up photo of adult Oregon Silverspot butterfly
A Silverspot and a bumblebee share a native Indian Thistle (Cirsium edule) bloom

Paul updated me on his survey, reporting that he had found over 1400 Silverspots, and he said overall they were doing pretty well. On one of the wetter meadows, he showed me where mechanical vegetation management was helping not only the Silverspot's larval host plant, but also an important native nectar plant, Indian Thistle (Cirsium edule). Within a couple years of the vegetation management intervention, the Silverspots began to show up, and today they are abundant there.


As we walked around the sites, I peppered him with every greater fritillary question that had been rattling around in my mind of late. One topic was my curiosity as to why I found eight Coronis Fritillaries in Lane County after never seeing one in Lane County previously. Paul described the intense drought conditions he'd recently seen in eastern Oregon, and the virtual absence of nectar sources in large areas. He conjectured that these Coronis Fritillaries had flown west in search of nectar for their very survival. Paul noted that while we often think of the importance of larval host plants for the survival of butterflies, the nectar plants they need are equally important. The meadow where we stood, with it's robust patch of Indian Thistle, was a case in point. I saw more Silverspots there than in the other two larger meadows combined.


Close-up photo of adult Hydaspe Fritillary butterfly
Hydaspe Fritillaries (Coast Range segregate of Argynnis hydaspe) in this area are quite large.

Paul pointed out a Hydaspe Fritillary (Argynnis hydaspe) and noted that Hydaspes at Mt. Hebo are notably larger than those in the Cascades. I had noticed that right off-- they were so large that at a distance I had at first wondered if they were Great Spangled Fritillaries (Argynnis cybele).


Close-up photo of adult Oreas Comma butterfly
The dark and mysterious Oreas Comma (Polygonia oreas silenus)

Before Paul headed off to finish up his work for the day, he mentioned that this area was quite good for the very dark western subspecies of the Oreas Comma (Polygonia oreas silenus) but that they usually came out a bit later in the year. Only minutes after Paul left, I spied a freshly eclosed Oreas clinging to a thistle stalk across the meadow a ways. As I walked over to get closer for a photo, it flew zig-zag fashion to a conifer tree at the edge of the meadow. Sitting there perfectly still, as if believing it was invisible, it let me get very close, and take several photos.


At the end of the day, I was quite contented to have finally photographed the other "Oregon" butterfly, after finally capturing the Oregon Swallowtail this past spring. My chance meeting with the affable and humble Paul Hammond was a wonderful surprise. I headed home better acquainted with the Silverspot and it's Mt. Hebo home than I had expected to. Now I'm looking forward to getting a copy his updated and explanded book on Colias sulphurs, co-authored by Dave McCorkle.


Here is my species list for the day (9 species):


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