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.