The Eastern Firefly (Photinus pyralis), also called the common eastern firefly and big dipper firefly, is the most common species of firefly in North America. It is a flying and light-producing beetle with a light organ on the ventral side of its abdomen. This organism is sometimes incorrectly classified as Photuris pyralis, which likely results from mistaking the similar-sounding genus Photuris (the femme fatale lightning bugs).

The femme fatale lightning bug female may also lure a common eastern firefly to be eaten to obtain spider-repellent steroids called "lucibufagins". In males the light organ covers the entire ventral surface of the 3 most posterior segments and in females it only covers a portion of the third posterior segment. These fireflies are most noticeable around twilight, in the early part of the evening and hover close to the ground. The species' common name refers to the characteristic flight of the male, which flies in a J-shaped trajectory, lighting on the upswing. During flight, the J-shaped flight pattern is used in combination with patrolling flash patterns while seeking a mate. Their flashes are stimulated by light conditions, not by rhythmic impulses as originally thought.

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