The female predator uses the mating signal to prey on the male of the other species. Eisner said the firefly species Photinus produces a chemical compound called lucibufagins. When these bugs are attacked by birds or spiders, lucibufagins flows on their outer shell. The chemical causes the predators to spit out the fireflies, often unharmed. On a typical dark night in June through August, fireflies seek mates through coded flashing.
Males flicker a unique pattern, and females of their species make a coded response.
When he spots the signal, a male flies quickly to the female, and the next generation is on the way. Eisner said the Photuris female has learned to imitate the courtship code of the Photinus female. The flash signal attracts Photinus males, and the Photuris female grabs 'em and chews 'em up. After eating the male, the female predator is able to bleed lucibufagins and thus is protected from other predators. The female Photuris even shares the chemical with a male Photuris during mating, he said.