By Nathan Brockman
Reiman Gardens
Iowa State University

Within the Christina Reiman Butterfly Wing at Reiman Gardens, resides a family of butterflies called Longwings (Heliconius). During the day, these active butterflies entertain guests as they fly from flower to flower, but little do guests know that each evening the Longwings participate in another fascinating behavior known as communal roosting.

Circadian communal roosting in butterflies occurs when a number of butterflies gather to rest for the night, typically on a single branch. These communal roosters can be quite numerous and can consist of a single specie or a variety of species. Each evening, the air around the roosting site fills with butterflies as they fly back and forth and work to find an open spot on the roost. The whole process takes about an hour to complete because the new arrivals tend to agitate the butterflies that perched earlier. Unless the roosting site is disturbed, the same butterflies will visit that spot night after night.

Strength in numbers is one of the benefits of communal roosting for Longwings. Predators dislike the taste of Longwing butterflies, so if a predator eats from the roost it will quickly learn not to do it again, saving the group.

Christina Reiman Butterfly Wing visitors can observe this behavior but there is a catch. As the days lengthen and the sun sets later each evening, the opportunity to observe roosting slips away because soon the sun will set well after the butterfly wing has closed to the public. So while the days are still short, come out to the Gardens to see the Longwing butterflies nightly dance.