Brachysternus prasinus

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Brachysternus prasinus is a green scarab beetle about 11–19 mm long, found in Chile and parts of Argentina. Its color and hair patterns vary a lot, and it is often used as a reference species when studying its genus. The insect lives in Nothofagus forests, from Valparaíso to Magallanes in Chile and into Neuquén and nearby Tierra del Fuego in Argentina, from sea level up to about 2,000 meters.

Adults fly mainly at dusk and are attracted to lights. The larvae feed on roots and decaying wood, and the species has an annual life cycle: eggs → larvae → pupae → adults, with adults typically present from November to February (peak flight in late December). Males and females differ in a few body features, such as a ridge on the male abdomen and a notch on the female's terminal segment. There is a lot of natural variation, with several morphotypes described from different areas, though many scientists treat these as part of the same species.

B. prasinus is considered a subterranean pest because larvae can damage crop roots (notably wheat) and adults can feed on aboveground plant parts. Control options include chemical treatments and biological approaches like using pathogens or pheromones.