Thursday, September 15, 2016

Lesser (but not least) Fritillaries

It was brought to my attention a while back by a reader that, while I've posted several items on identifying Greater Fritillaries (Speyeria species), I haven't posted anything on Lesser Fritillaries (Boloria species). To review, please see my Fritillary Frenzy post. You'll notice I mentioned that people were starting to use Argynnis as the genus of greater fritillaries, however that has since been back-tracked, or at least put on the back burner for now, and the official name is still Speyeria. As I wrote in the 2013 article, fritillaries can be divided into two groups: greater and lesser. As the names suggest, greater fritillaries are larger, usually with a wingspan between 1.5 and 3 inches, compared to the 1 to 1.5 inch wingspan of lesser fritillaries.

There are six species of Boloria in the Pacific Northwest. These links will take you to the Butterflies of America page for each species.
Boloria selene Silver-bordered Fritillary
Boloria freija Freija Fritillary
Boloria chariclea Arctic Fritillary
Boloria epithore Western Meadow Fritillary
Boloria bellona Meadow Fritillary
Boloria astarte Astarte Fritillary

Lesser fritillaries are easy to tell apart from each other compared to their larger cousins, therefore I won't go into much detail about each one. As you can see by the images below, the dorsal side is similar between these species, so a clear view of the ventral side is usually necessary for a positive identification.
Ventral (underside) comparison of the six Boloria species found in the Pacific Northwest.

Silver-bordered Fritillary Boloria selene
Although common in parts of Canada and elsewhere in its range, this species is relatively rare and localized in WA and OR and is listed as a State Candidate in WA and Imperiled in OR. It is easily separated from other Boloria species by the silvered spots scattered across the ventral side of its wings.
Silver-bordered Fritillary (Boloria selenemale and female

Freija Fritillary Boloria freija
Freija is primarily found in Canada, but can be found in a narrow strip of high-elevation willow bog habitat in north-central Okanogan County, WA. It is identified by the distinct white tooth or fang-mark on the center of the ventral hindwing and a bold black zig-zag across the median.
Freija Fritillary (Boloria freija) male and female

Arctic Fritillary Boloria chariclea
This species is truly an arctic butterfly, found across the entire northern hemisphere, from Europe and Siberia to northern North America. It is also known as the Purplish Fritillary. In the PNW it is only found in the WA Cascades and Olympic Mountains. It is similar to Freija, but has a pale submedian band without a distinct "tooth" and lacks the dark zigzag median pattern on Freija.
Arctic Fritillary (Boloria charicleamale and female

Western Meadow Fritillary Boloria epithore
These are the most widespread and common of the Boloria species in the Pacific Northwest, found in nearly any forest habitat from the Cascades to the coast, and portions of the north, northeast and southeast edges of Washington and the northeast corner of Oregon. They are identified by the "soft" ventral pattern with subtle shades of purple, pink, brown and orange, mostly separated into an outer purplish band and inner yellowish-orange bands, compared to the checkered and zig-zag patterns of the other species except B. bellona (shown next), which is generally more brownish and has angular wings. 
Western Meadow Fritillary (Boloria epithore), two males

Meadow Fritillary Boloria bellona
Meadow fritillaries are primarily found around the Great Lakes and northeastern United States south to Tennessee, but are also found in portions of the Rocky Mountains and scattered populations in the Blue Mountains of NE Oregon and in eastern and north-central Washington. They are identified by their squared-off wing tip on the forewing, and slightly angular hindwing, compared to the rounded wings of the other Boloria species shown here. The ventral hindwing pattern is a marbled brown and purplish-brown pattern similar to B. epithore (shown above), but lacks the defined separation between the outer purplish band and inner yellowish-orange bands seen on epithore.
Meadow Fritillary (Boloria bellona), two males

Astarte Fritillary Boloria astarte
Although this species is considered one of the "lesser" fritillaries, it is the size of average "greater" fritillaries such as Zerene or Callippe. It is very uncommon, found in parts of Alaska and Canada, and only in the highest elevation talus slopes of Whatcom, Okanogan and Chelan counties in Washington and Flathead, Teton, and Glacier counties in Montana. The best place to see it in Washington is at Slate Peak on the Okanogan/Whatcom county line, but you must arrive there very early in the day if you want any hope of photographing or catching one, as they warm up quickly on the rocks. I tried to find them for the first time this year in late August; while I did finally get a good look at one, and a few glances at two or three others, I was never able to get close enough to catch or photograph any of them, they're super skittish!
Astarte Fritillary (Boloria astartemale and female

As I noted at the beginning, I wrote this article because of a question from a reader. If you would like to see a species profile for a particular butterfly or group of butterflies, or learn more information about some other Lepidoptera topic, let me know! I have a new public email address specifically for correspondence related to this blog, see the "How to contact me" strip to the left.

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