Carleton University holds an annual butterfly show each Fall. It takes place in a greenhouse of the Nesbitt Biology Building and is open to the public on a donation basis. The RA Photo Club arranged for 30 members to have access for a short period before the public was admitted. I was one of the lucky 30 and had a marvelous time trying butterfly shooting for the first time.
We were warned that the greenhouse would be hot and humid. Was it ever! The small greenhouse was also crowded with club members, but we all tried to keep out of each other's way. I chose to use my 100 - 400 mm lens, and that worked well. But, there were times in the tight space when the butterflies were too close for me to focus on. It was very much a case of picking the shots to suit the lens.
I'd love to do this again if the opportunity is available!