observations through the seasons

In visiting a new shrub steppe site this spring, I found a bountiful array of early blooming flowers, including several buckwheats and the sagebrush violet, Viola trinervata. The latter is a host plant for the Coronis Fritillary, Argynnis coronis. I made a mental note of this for later reference.

The Coronis is one of Washington’s first fritillaries to emerge in the spring after overwintering as first instar larvae in the shrub steppe and lower canyons. In areas that I frequent in central Washington, they burst onto the scene with fresh orange coloring and high energy in early May. Their appearance is celebrated by many in our WBA community. I’ve marveled at their arrival each spring and their remarkable journey as the season progresses.

After emergence Coronis begin an altitudinal migration to higher elevations where nectar is more plentiful as the shrub steppe soon becomes hot and dry. During the summer they may be seen in high mountain meadows sur- rounding the Columbia Basin and beyond. Some years they are seen in the subalpine meadows of Mt. Rainier National Park. In late summer the species returns to the shrub steppe for egg laying. Their seasonal migration has been documented by David James and Jon Pelham (The Journal of the Lepidopterists’ Society, 2011).

The appearance of Coronis once again at lower, now dry, locations is a sign to me that the season is drawing to a close. Rabbitbrush is the primary nectar source remaining and is a butterfly magnet at this time. Coronis and other late season species may be seen in large numbers on the plant. Nectar is critical to sustain Coronis for the last and most important job of egg laying.

Their abundance this past September was a marvel to observe. When I reported to Jon Pelham the large number of Coronis I was seeing this fall, he nudged me to search for egg laying activity. The mental flag I planted in the spring when observing the sagebrush violets started waving.

On returning to the “new” shrub steppe site, the dry bushes and desiccated plants presented a very different landscape than what I had seen earlier in the season. The sagebrush violet, critical for Coronis larvae, had senesced by this time with only pale dry leaves remaining. But I was amazed to see Coronis flying in the area. Fueled with nectar from nearby rabbitbrush, individuals were on the wing as I walked out to the site and at the location itself where within an hour I detected 10 female Coronis exhibiting egg laying behavior. (Additional individuals were seen after the first hour.) Females flew several feet above the ground, periodically dropping to the substrate composed of dirt, dry plants, twigs, rocks, dried grasses and the senesced violets. After a brief amount of time at one site, another location would be visited a short distance away. It was fairly easy to follow these females from site to site for observation and photos. Through their own means they located the desiccated violet plants that would provide fresh spring growth for larvae after leaving diapause in the spring.

David James suggests, “It must be volatiles given off by the dead and drying violets…it couldn’t be a visual thing.” Although I didn’t see each individual ovipositing, I observed a few doing so. I’m confident that either egg laying or surveying for a potential site is what was occurring. The behavior of the females was enthralling, and I let them lead me around the area as they went about the important task of laying this season’s eggs. I visited the area on two additional dates and observed the same behavior, but with fewer and more worn individuals present. The eggs hatch soon after being laid, and the first instar seeks a place of safety for diapause during the cold season ahead. Needless-to-say, I was excited to be able to observe this final act of the adult Coronis which also marks the beginning of next year’s brood!

Butterfly abundance in the warmer months is celebrated and enjoyed by many of us. Seeing the rabbitbrush in full bloom and alive with activity every fall is a marker for me that the season is once again changing. Although mostly out of sight, the fall season’s quieting for the next stage of metamorphosis is also remarkable. A wealth of life rests in the detritus of steppe and forest, under rocks, in tree bark, and other concealed locations during the cold season. The rabbitbrush party is a great way to celebrate this annual transition. And for Coronis, egg laying seals the deal for the emergence of a new generation next spring.

As always, I am grateful to our experts who so generously share their wealth of knowledge. And also, thanks to Vicki and Mike Elledge who excitedly directed me to the shrub steppe site above.

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All Photos by Melanie Weiss