Fireflies, beetles of the family Lampyridae, use flashes of bioluminescent light for sexual communication—by means of coded patterns, males and females identify and locate each other in darkness1. In sexual signalling of Photinus macdermotti (eastern United States) the male emits two flashes separated by ∼2 s and the female then waits ∼1 s before replying with a single flash (Figs 1a, 2a)2. Females of Photuris versicolor and Photuris ‘B’ mimic the reply of P. macdermotti females thus attracting P. macdermotti males, which they eat (Fig. 1b, c). When the predators are decoying P. macdermotti males, they sometimes produce ‘extra’ flashes that mimic the ‘competition’ flashes used by the males when competing for females (compare Fig. 1d with e)3. I suggest here that the male competition flashes (that the predators mimic) might also be mimics of the predator's own mimicry.