The orange sulphur, Colias eurytheme, is a fairly common butterfly found at the arboretum and throughout North America. Its range includes southern Canada, coast to coast of the United States, and down into Central Mexico.
I took this photo in mid July by the river and I remember feeling fortunate to have gotten this shot. They often landed where it was tricky to get a photo of them and they seemed easily startled when I tried to move closer or to get a better angle for the photo.
I imagine this butterfly gets its name from the chemical element sulfur that is a pale yellow or greenish-yellow in color. Sulphur refers to the same element and is the traditional spelling in British English. Along with its graceful color, the other key identification feature is the distinct white spot encircled by two pinkish-brown rings on the underside of the hindwing. All the descriptions of this butterfly I found also mentioned a small satellite spot adjacent to this larger spot, but it is notably missing from the one I photographed here. Also, look for a row of subdued, submarginal black or brown dots on both the hind and forewings.
I only saw this butterfly land and rest with its wings closed, folded back behind its body revealing the underside. If by chance you get a glimpse of the upper side, you will be able to discern the male from the female. The males are bright orange with an unbroken black border. The females are either bright orange or greenish white with “window” spots breaking up the black border. The wing flutters of this butterfly are fast enough so that I only could catch a glimpse of a fleeting flash of color or the black border of the upper side.
They are found in open habitats such as prairies and agricultural fields. At the arboretum I frequently see them in the south meadow and the open gravel bars along the river. Their host plants are many members of the pea family like lupine, vetch and clover that can be found at the arboretum. The pocket guide Butterflies of Lane County created by the Eugene-Springfield chapter of the North American Butterfly Association (NABA) says that they fly late March to early November with peaks in July and September. So still be on the lookout for this beautiful, bouncing butterfly bounding by.
Resources
“Orange Sulphur | ButterfliesofOregon.” Butterflies of Oregon, https://www.butterfliesoforegon.com/colias-eurytheme. Accessed 14 Aug. 2026.
Orange Sulphur (U.S. National Park Service). https://www.nps.gov/articles/000/orange-sulphur.htm. Accessed 14 Aug. 2026.
I also referenced the pocket guide Butterflies of Lane County by the Eugene-Springfield NABA Chapter compiled by Marta Makarushka.