Fluorescence in fireflies (Coleoptera: Lampyridae): using sentinel prey to investigate a possible aposematic signal

While fireflies are most renowned for their bioluminescent signals, several species also have been shown to possess UV and blue-induced fluorescence. In a field study, we used a sentinel prey approach to investigate whether this trait might serve as an aposematic function in chemically defended fireflies. We also examined and provide the first detailed description of green and red patterns of blue light-induced fluorescence in the adults and larvae of Ellychnia corrusca (L.) (Coleoptera: Lampyridae). We placed artificial prey models with and without fluorescent markings in a forested area of Belmont, Massachusetts, USA, where they were exposed to natural predators. Clay models were styled to resemble Photinus fireflies, the most common firefly genus in this area, and a close relative of Ellychnia. The field study was conducted from Oct through May in Belmont, Massachusetts; this is the period when adults of the diurnal non-luminescent firefly E. corrusca are overwintering on trees. We observed considerable seasonal variation in attack rates, and marks on the clay models indicated they were attacked by avian, mammal, and arthropod predators. However, no difference was seen between fluorescent and non-fluorescent models in predator attack rates. This suggests that fireflies' fluorescent markings do not serve as an aposematic signal, at least for the predator guild active in New England woodlands.