Most people are probably familiar with firefly beetles (Coleoptera: Lampyridae). In the United States they’re particularly common in the south and east during early summer. Although not all firefly species can create light, those that do illuminate the warm nights with their characteristic yellow-green flashes. Produced by chemical reactions within specialized organs, these signals are normally used to attract mates. Fireflies in the genus Photinus are perhaps those most frequently observed.
Some other fireflies, however, can also use their flashing signals for more nefarious purposes. Females in the genus Photuris can imitate the flashes of Photinus females, attracting Photinus males with the promise of sex.
When Photinus males are within reach the larger Photuris females devour them. While the predatory females obtain nutrition from their prey, it’s been shown that they gain another benefit as well.
Relatively harmless Photinus fireflies produce defensive chemicals known as lucibufagins that make them distasteful to most predators. Photuris fireflies lack the ability to synthesize these compounds, leaving them potentially vulnerable. By eating the Photinus males Photuris females gain their defensive capabilities.
In spite of their welcome summertime flashing and seemingly harmless nature, even these insects are in a constant struggle among each other for survival.