Fireflies at one hundred plus: a new look at flash control

The mysterious process by which fireflies can control theirflashing has inspired over a century of careful observationbut has remained elusive. Many studies have implicated oxygenas the controlling element in the photochemical reaction, andthe discovery of nitric oxide synthetase (NOS) in the lanternhas suggested that nitric oxide (NO) may control oxygen accessto the light-emitting photocytes, thereby triggering the flash.However, there are several drawbacks to oxygen as a controllingagent, and in view of the prominence of peroxisomes in lanternmorphology and biochemistry, we suggest that it is hydrogenperoxide that triggers the flash, and we present a model bywhich this may take place.