Zerene Fritillary (Speyeria zerene)
No, we didn’t go overboard with the color saturation on the photo of this week’s crawly; the zerene Fritillary (Speyeria zerene) really is that vibrant!
That is to say, at least this one was. Zerenes run the orangey rainbow from a non-retina burning warm orange to this grab-your-sunglasses impossibly brilliant red-orange.
Zerenes are on the wing in July, August and September. This one was spotted in late July, so they were probably newly eclosed (hatched) which factors into their POP of color (along with the natural variation).
Fritillaries in general are pretty special butterflies with their fiery colors and funky, loopy flight patterns. Zerenes are doubly cool because they are only found in the Northwest United States. Additionally, three subspecies of zerene fritillaries are endangered, including Oregon’s own Oregon silverspot butterfly (Speyeria zerene hippolyta) who have been federally listed since 1980.
How rare is the silverspot? Out of 318 observations of zerenes on iNaturalist, 77 are silverspots. Generally, silverspots are spotted on the coast, but there is one inland sighting in our area.
The main reason for the decline of zerene species is the loss of their main foodplant due to development and control of coastal properties.
All zerene caterpillars are particular eaters, feeding only on low growing violets including pine violets (viola lobata), streamside violets (viola purpurea), wedgeleaf violet (viola cuneata) and goosefoot yellow violet (viola pinetorum). However, for silverspots the early blue violet (viola adunca) is crucial to their survival.
Female zerenes lay their eggs in late summer/early fall in, on or close to the stems of the host plant. There must be a relative abundance of early blue violets in spring so the caterpillars can find and feed on them. The caterpillars grow to their first instar, then go into diapause (a period of suspended development in insects) over winter. When they become active again in spring, they’ll need those early blooming violets.
On top of that, the caterpillars need shelter from high winds and rain and adults need enough wildflowers blooming in the area to provide nectar for them in the late summer and early fall months.
Currently there are seven different locations where Oregon silverspot habitats are being protected with help from the Nature Conservancy and U.S. Fish and Wildlife. Our neighbor Washington state is helping save our namesake silverspot by restoring populations close to the Oregon/Washington border as well.
Finally, zoos are rearing silverspots in captivity and releasing them in suitable habitats to help the wild populations along.
Zerenes in general can be found throughout Oregon, but the largest populations are along the Cascades. Our pictured flitter was dining on a mountain boykinia (Boykinia major) wildflower a couple of feet from the Rogue River in the Rogue River National Forest.
Inland zerenes like to live in meadows and open conifer forests as well as along forested roadsides. They like a mix of open space and forest for protection.
With a two-inch wingspan zerenes are considered “medium-sized” butterflies, but with their bold coloration the males especially can sure look larger as they fly about in dappled sun/shade.
As a rule, if you see a fritillary flitting frantically, you are looking at a male. While they do stop to fuel up now and then, they spend most of their time in flight patrolling for female fritillaries.
Because their bright hue is so eye catching, males have a loopy, zigzag flight pattern to confuse potential predators.
Zerenes and our other species of fritillaries will be out and about for at least another couple of months so be on the lookout for a blaze of orange on the wing while you’re out enjoying our more temperate late summer, early fall temperatures.