Examining the Role of Cuticular Hydrocarbons in Firefly Species Recognition

During animal courtship, multiple signals transmitted in different sensory modalities may be used to recognize potential mates. In fireflies (Coleoptera: Lampyridae), nocturnally active species rely on long-range bioluminescent signals for species, sex, and mate recognition, while several diurnally active species rely on pheromonal signals. Although in many insects non-volatile cuticular hydrocarbons (CHC) also function in species and sex discrimination, little is known about the potential role of CHC in fireflies. Here, we used gas chromatography to characterize species and sex differences in the CHC profiles of several North American fireflies, including three nocturnal and two diurnal species. Additionally, we conducted behavioral bioassays to determine whether firefly males (the searching sex) were differentially attracted to extracts from conspecific vs. heterospecific females. Gas chromatography revealed that nocturnal Photinus fireflies had low or undetectable CHC levels in both sexes, while diurnal fireflies showed higher CHC levels. No major sex differences in CHC profiles were observed for any firefly species. Behavioral bioassays demonstrated that males of the diurnal firefly Ellychnia corrusca were preferentially attracted to chemical extracts from conspecific vs. heterospecific females, while males of the remaining species showed no discrimination. These results suggest that while CHC may function as species recognition signals for some diurnal fireflies, these compounds are unlikely to be important contact signals in nocturnal Photinus fireflies.