Butterflies at porch lights: Exploring nocturnal light visitation in butterflies using community science data from <scp>iNaturalist</scp>

Abstract Artificial light at night (ALAN) is altering natural light conditions globally, with dramatic effects on insect behaviour. Flight‐to‐light behaviour is one of the most noticeable and ecologically significant impacts. Research has focused on nocturnal and crepuscular insect taxa, but diurnal insects also exhibit flight‐to‐light behaviour. Community science is increasingly recognised as useful for biological research. iNaturalist is an unstructured community science project where observations are geo‐tagged photos of organisms. We downloaded iNaturalist observations of butterflies at artificial light sources in the United States and Canada. We manually verified that observations were from light sources and recorded light source information. We examined light visitation in butterflies and checked for signals of natural history traits predicting light visitation at a species level. We compiled 384 observations of butterflies at light sources, representing 107 species, 74 genera and all six diurnal butterfly families. Most observations came from residential light sources or insect sampling/observation schemes (e.g., moth sheets). Observation frequency at lights varied across butterfly families: Lycaenidae were observed the most and Papilionidae the least. Habitat preference may influence light visitation: closed‐habitat species were observed more frequently than open‐habitat species. There were no clear relationships between observation frequency and wingspan or migratory behaviour. A broad diversity of butterflies has been observed at artificial light sources. Butterfly species differ in the frequency with which they are reported at light sources on iNaturalist. Natural history traits may be useful in predicting a species' vulnerability to ALAN.