In Search of Shivering Butterflies

On Wednesday afternoon I played hooky from work. I have been wanting to photograph two rare butterfly species: the Olympia Marblewing and the Hoary Elfin. Both are found in sandy dune habitats and have brief flight periods early in the season. Illinois Beach State Park, on Lake Michigan up near the Wisconsin border, hosts ample populations of both species. Wednesday was a beautiful summery day- sunny with temperatures well into the eighties. I thought that it would be the perfect time for a photo trip.

Foggy Dunes

Illinois Beach State Park is somewhat notorious for having cold weather. I checked Weather.com before I left work and learned that it was mostly sunny and 75° up at the park. "OK," I thought, "cooler near the lake- but still plenty warm for butterflies." By the time I made the hour-long drive out there the wind had shifted off of the lake. It was foggy and my thermometer was reading 57°, even though it was still in the 80s at O'Hare Airport. Conventional wisdom has it that butterflies begin becoming active when temperatures reach or exceed about 65°, and then only if it's sunny out. I cursed my luck thinking I had wasted an afternoon.

Hoary Elfin (Callophrys polios)

The day ended up being a lesson on the limits of conventional wisdom. It was less than five minutes after I sent a complaining text to a friend that I saw my first Hoary Elfin.

Bearberry (Arctostaphylos uva-ursi)

Caterpillars of Hoary Elfins feed only on bearberry leaves and flowers. Bearberry is an extremely rare plant here in Illinois, so it's really not surprising that this butterfly is on the state endangered species list.

Hoary Elfin (Callophrys polios)

As I continued wandering through the dunes, I started seeing more and more elfins- over a dozen in very suboptimal conditions. I even encountered a mating pair!

Mating Elfins (more insex for Rodger)

As excited as I was to be finding elfins, I really wanted some photos of Olympia Marblewings. I have one digital image of a hoary elfin from last year. It isn't the best photo, but it's sufficient for use in talks. In contrast, my only marblewing photos are from at least a decade ago, and they are on film. Unfortunately, I wasn't seeing any.

Olympia Marblewing (Euchloe olympia)

Finally, I noticed that one of the white sand cress flowers seemed unusually large and yellowish. Moving in to check a bit more closely, I found a marblewing, torpid in the cold. The chilly weather that I was cursing when I arrived at the park ended up helping me out by keeping the butterflies calmer and less active. I could approach close with the camera and take my time composing shots. I only saw 3 marblewings on this trip, but managed to get decent shots of both upper and under surfaces.

Olympia Marblewing (Euchloe olympia)

As I already mentioned, Illinois Beach State Park has a reputation for being unusually cold during the spring months due to its proximity to the lake. Both of these species of butterflies have very brief flight periods that coincide with this unpredictable and often quite chilly weather. It's possible that their willingness to fly under such poor conditions may be a survival adaptation that allows them to persist through years with very little good weather during their flight time.

Dunes in Illinois

Since I recently blogged about the wonders of the dune community in Indiana, it's only fair that I give some time to the sand dunes of Illinois Beach State Park. The park extends along the Lake Michigan shoreline right up near the Wisconsin border. The dunes are smaller here than in Indiana or Michigan. That's because the prevailing westerly winds blow a lot of the sand out into the lake rather than into or along the shore. The latter process is necessary to sculpt taller dunes.

Bearberry (Arctostaphylus uva-ursi)

Two rare butterflies are found at Illinois beach. They fly very early in the season, so on Friday afternoon, I made my way up to the park to attempt to find them. The Hoary Elfin is an endangered species in Illinois. The caterpillars feed exclusively on bearberry, a rare plant in Illinois. The population of Hoary Elfins at Illinois Beach is the only one known in the state.

Bearberry is a woody plant that grows in prostrate mats

Curiously, Hoary Elfins have never been reported from the Indiana Dunes, despite the existence of ample host plant in apparently similar habitat.

Friday afternoon was very windy, which helped neither the the butterfly watching nor the photography. I only saw about a half dozen elfins. The constant motion of even very low vegetation in the stiff breeze meant that most of my photos were blurry. I did manage to get one decent image.


I was keeping an eye out for tiger beetles during my visit, and only managed to see one. It's a terrible photo, but represents the only time I've ever seen Cicindela scutellaris in Illinois. This one is subspecies lecontii.

Festive Tiger Beetle (Cicindela scutellaris lecontii)

The other butterfly that I was seeking, the Olympia Marblewing, was a no show. I suspect that the wind was just too high. Despite the suboptimal conditions, it's really hard to have a bad day at such a beautiful nature preserve. I even managed to continue my project of trying to get more digital images of butterfly species that I need to include in talks. Just before I reached the parking lot to leave, an American Lady posed very briefly for me. Up until now, my only images of that species have been on film.

American Lady (Vanessa virginiensis)

Misty Savanna

Black Oak Sand Savanna with Showy Goldenrod

Last week, Vincent and I had to go up to the conference center at Illinois Beach State Park to make a presentation to the board of the Illinois Nature Preserves Commission. We were (successfully) seeking approval for a permit to release Silver-bordered Fritillaries onto the nature preserve at Gensburg-Markham Prairie (something that is now done). I have made presentations to this board before, and in common with my previous experiences I found something that sounds very bureaucratic is actually a reasonably pleasant process.

Ecotone between the Oak Savanna and a Swale

After our presentation at the meeting, Vincent and I went off for a walk into the park. Illinois Beach is a very large (4,160 acres) remnant of native Lake Michigan shoreline. Vincent had never been to this park before, and I enjoyed introducing him to this amazing spot. The day was cloudy and misty, and had a decidedly melancholic autumnal feel to it.

The Dead River

The park is a dune and swale complex. The Dead River occupies one of the swales. It gets its name because it is usually separated from Lake Michigan by a sand bar. Periodically, pressure in the river builds up, and the water overflows the sand bar and empties into the lake.

Sky Blue Aster

We were treated to an array of autumn wildflowers as we walked. Illinois Beach State Park is in my top five natural areas in Illinois that I recommend visiting.