Firefly Radiance Revisited

Researchers have co-opted fireflies' twinkle for experimental readouts in forensic, cellular, and other studies, but full details about how the insects glow remain unclear. Now, Yoriko Ando and Hidefumi Akiyama at the University of Tokyo and coworkers have used their recently developed chemiluminescence spectrometer to reexamine firefly bioluminescence (Nat. Photonics, DOI: 10.1038/nphoton.2007.251). The team assessed fireflies' luminescence quantum yield—that is, the efficiency of the insects' lanterns. The new, more accurate value is half of the previously accepted 50-year-old measurement, but fireflies still rank as better light producers than other luminous creatures, such as jellyfish. The researchers also revisited the mechanism of pH-dependent color changes in firefly light emission. The results suggest that the dominant green emission decreases at lower pH, which allows the relatively constant red emission to shine through. Other experts contend that more research is needed to confirm those color-change observations, noting also that the new technology could help fine-tune knowledge about bioluminescence.