Timarcha is a genus of leaf beetles in the family Chrysomelidae, with more than 100 described species in three subgenera. The most widely known species is T. tenebricosa, the bloody-nosed beetle. All species are black, wingless organisms. Timarcha are herbivorous species, living mostly on plants belonging to Rubiaceae and Plumbaginaceae, although a few can feed on Brassicaceae and Rosaceae. Timarcha is the only member of the tribe Timarchini.
Beetles of the genus Timarcha are flightless leaf beetles, widely recognized for their distinctive black appearance and their defensive mechanism of "reflex bleeding" of a bright red, foul-tasting hemolymph when threatened.
Key Facts About the Genus Timarcha
Appearance: All species in the genus are entirely black, often with a bluish sheen, and have a dome-shaped body. They typically measure between 10-20 mm in length.
Flightless: Their elytra (forewings) are fused together, rendering them incapable of flight. This is considered an apomorphic (derived) character.
Defense Mechanism: They are popularly known as "bloody-nosed beetles" in Europe because they ooze a red, distasteful liquid (hemolymph) from their mouths when disturbed. This toxic fluid deters predators such as birds and lizards. North American species, being primarily nocturnal, do not exhibit this specific behavior.
Diet: Timarcha species are herbivorous and generally specialize in feeding on plants from only a few families, most commonly Rubiaceae (e.g., bedstraws like Galium verum and Galium mollugo) and Plumbaginaceae. North American species mainly feed on Rosaceae, such as strawberry and bramble bushes.
Distribution: The genus has a unique disjunct Holarctic distribution, with the majority of species in the Western Palaearctic region (Europe, North Africa, Western Asia) and a few species along the west coast of North America (British Columbia to California).
Habitat: They inhabit a broad range of environments, including high mountains, humid forests, grasslands, and sandy coastal areas.
Life Cycle: They are long-lived as adults (up to 10-14 months) and typically have an annual, univoltine life cycle. Larvae and adults feed on host plants, with pupation occurring in the soil.
