Ellychnia is a genus of fireflies. First defined by Émile Blanchard in 1845, the genus contains 12 species, which are widespread in the United States. Adults are black, with rose-colored marks on the pronotum;sexual dimorphism is unknown. These beetles are active during the day, and have no light-producing organs as adults; instead, they attract mates using chemical signals. The larvae of Ellychnia fireflies live in rotting logs.