In 1983, I was part of a research team to study the monarch butterfly migration from North America to Mexico. All of the monarchs east of the Mississippi River from as far north as Canada fly to the Sierra Madre Mountains and overwinter there. None of them had ever been there before. In the spring, they return and repopulate the eastern U.S. and Canada. Many generations later, in September, they repeat the cycle. Throughout the summer, adult monarchs live 7 to 10 days except the generation that overwinters in Mexico. Those individuals live 6 months. I took this shot of the butterflies in their dormancy with a medium format film camera, the Mamiya RB 67, and a powerful Metz CT-60 flash. It was quite dark in the forest, and I was shooting Ektachrome 64 transparency film at the time. 64 ISO and a maximum lens aperture of f/4.5 meant a flash was necessary to provide enough light for a sharp picture. Otherwise the shutter would have been too slow. A tripod wasn’t feasible because the branches on which the monarch butterflies clung were always moving slightly. I used a 350mm Mamiya lens which was equivalent to a 200mm telephoto in the full frame 35mm digital format. My shutter would have been 1/250, and the aperture was probably f/5.6 or f/8.